Gallium nitride based laser dazzling method

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 13/752,158, filed on Jan. 28, 2013, which is a continuation of U.S. patent application Ser. No. 12/787,343, filed on May 25, 2010, which claims priority to U.S. Provisional Patent Application No. 61/182,104, filed on May 29, 2009, each of which is incorporated by reference herein for all purposes.

BACKGROUND OF THE INVENTION

The present invention is related to laser devices. More specifically, embodiments of the present invention provide laser dazzling devices powered by one or more green laser diodes characterized by a wavelength of about 500 nm to 540 nm. In various embodiments, laser dazzling devices include non-polar and/or semi-polar green laser diodes. In a specific embodiment, a single laser dazzling device includes a plurality of green laser diodes, which may couple power together. There are other embodiments as well.

As human beings become more civilized, non-lethal techniques have been developed to temporarily halt others that may be dangerous or hostile. In any potentially hostile situation such as a military security checkpoint, a critical need exists to identify potentially threatening individuals or groups prior to undertaking an escalation of force. Non lethal threat detection and deterrent techniques are commonly used such as megaphones, tire spike strips, traffic cones, fencing, and hand gestures. However, many of these are impractical in impromptu security environments, and such measures may not show enough force to deter potentially hostile parties. If a serious threat is anticipated, historically, warning shots were fired, but this action can actually accelerate tensions and result in unwanted and unnecessary escalation of force if the shots are perceived incorrectly by the approaching party. Moreover, once the warning shots have been fired, a common next step in the escalation of force is to engage the approaching party directly with gunfire which dramatically increases the likelihood in loss of life.

As a result, an intermediate means of threat detection using bright light has been developed and employed called laser dazzling. This measure provides less than lethal threat detection, assessment, and an opportunity for de-escalation while at the same time providing a strong visual warning which can “dazzle” or induce temporary blindness to disorient approaching hostile parties without causing permanent ocular damage. End users of these tools include soldiers on the battlefield, homeland security officers, police, general security who find themselves in any potentially hostile situation.

An application of bright light for threat detection and deterrent goes back to early in the 20th century when soldiers used searchlights for this purpose. As lasers were developed in the 1960s, they became more portable, and by the 1980s, defense and security forces were using lasers as dazzlers because of their long range capability resulting from their collimated beam output. In the 1990s, the United Nations enacted the Protocol on Blinding Laser Weapons which outlawed weapons intended to cause permanent blindness, but which leave the door open to weapons which induce temporary blindness.

Laser dazzlers are a common tool in the defense and security market. They go by several names, including: laser dazzler, nonlethal visual disrupter, visual warning technology, nonlethal lasers, and others. In conventional laser dazzlers, green lasers are often employed. In order to generate the green laser light in the conventional laser dazzlers, a three stage laser is often required, typically referred to as a diode pumped solid state (DPSS) frequency doubled green laser. A conventional laser design typically includes:

• • A laser diode which outputs 808 nm laser light (typically powered by a battery)
  • The 808 nm laser is then focused into a solid state lasing crystal based on ND:YAG or Nd:Van. The crystals emit laser light at or near 1064 nm.
  • The 1064 nm is then incident on a frequency doubling crystal which creates green light through the second harmonic generation process where two 1064 nm photons are converted into a single 532 nm photon. The frequency doubling crystal is typically KTP, LBO, BBO, PPLN, or another similar material. While these conventional laser dazzling devices are functional, there are certain drawbacks. That is, conventional laser dazzlers are often complex and require complex optics and configurations. Additionally, such laser dazzlers are also expensive and difficult to scale. These and other drawbacks are described throughout the present specification and more particularly below.

Therefore, it is to be appreciated that improved systems and method for laser dazzling devices are desirable.

BRIEF SUMMARY OF THE INVENTION

According to the present invention, laser devices are provided. More specifically, embodiments of the present invention provide laser dazzling devices powered by one or more green laser diodes characterized by a wavelength of about 500 nm to 540 nm. In various embodiments, laser dazzling devices include non-polar and/or semi-polar green laser diodes. In a specific embodiment, a single laser dazzling device includes a plurality of green laser diodes. There are other embodiments as well.

In a specific embodiment, the present invention includes certain features for a laser dazzler as defined below:

• • Wavelength: Dazzlers are configured to output green light since the eye is most sensitive to green wavelengths. Specifically, for the same amount of optical power, the human eye is typically more than 5 times more sensitive to green light as compared to red or blue light in daylight conditions.
  • Power: Dazzlers output optical power ranges from 5 mW to 500 mW, depending on the range. It is noted that these power levels exceed the FDA's eye-safe power of a laser pointer (5 mW). As a result, the dazzler may be specified with a Nominal Ocular Hazard Distance (NOHD) which is the distance under which one can potentially cause eye injuries if used on anyone up to that distance. For example a dazzler may have an NOHD of 45 meters.
  • In addition to the laser, other features include telescoping optics to collimate the beam to a large or small spot at a given range, batteries, mechanics for handheld operation and integration with small arms, sighting, etc.
  • Minimal power consumption in order to minimize size, cost, weight of the battery and of the thermal management required.
  • Ruggedness over temperature, shock, vibration.
  • Compact size.
  • Lightweight.
  • Low cost.
    Of course, there may be other variations, alternatives, and modifications.

According to an embodiment, the present invention provides a laser dazzling apparatus. The laser dazzling apparatus includes a housing member. The laser dazzling device includes a laser device. The laser device comprises at least a gallium and nitrogen containing device having an active region and a cavity member. The laser device is configured to emit a laser beam having a wavelength about 500 nm to 540 nm. The active regions include gallium nitride material, the laser beam being characterized by a first direction. The laser dazzling device includes a driving circuit electrically coupled to the laser device. The driving circuit is adapted to deliver electrical energy to the laser device. The electrical energy is less than 800 mW. The laser dazzling device includes a power source electrically coupled to the driving circuit. The laser dazzling device includes an activation module electrically coupled to the driving circuit. The activation module is configured to send an activation signal to the driving circuit. The laser dazzling device includes a sight for aligning the laser beam to a desired position.

According to another embodiment, the present invention provides a laser dazzling device. The laser dazzling device includes a laser device. The laser device comprises a green laser diode. The green laser diode comprises an active region and a cavity member. The green laser diode is configured to emit a laser beam at an intensity level of less than 800 mW. The active regions includes gallium nitride material. The laser beam is characterized by a first direction. The laser dazzling device includes a driving circuit electrically coupled to the laser device. The driving circuit is adapted to deliver electrical energy to the laser device. The electrical energy is less than 800 mW. The laser dazzling device includes a power source electrically coupled to the driving circuit. The laser dazzling device includes an activation module electrically coupled to the driving circuit. The activation module is configured to send an activation signal to the driving circuit, the activation module comprising an electrical trigger. The laser dazzling device includes a sight for aligning the laser beam to a desired position. In an alternative specific embodiment, the present invention provides a laser dazzler apparatus. The laser dazzler apparatus includes a laser device including a laser diode. The laser diode comprises a gallium and nitrogen containing substrate configured in a semi-polar orientation in one or more embodiments. The laser diode is configured to emit a laser beam characterized by at least a wavelength of about 490 nm to 540 nm according to a specific embodiment. The apparatus includes a power source electrically coupled to the laser device in a specific embodiment.

It is to be appreciated that embodiments of the present invention provide numerous advantages over conventional techniques. According to the present invention, a laser dazzling device implemented using one or more green laser diodes based on GaN technology has numerous advantages over existing DPSS approaches.

Efficiency: Because the GaN diode laser is a single stage, it is inherently more efficient and therefore requires less powerful batteries, decreasing the size, weight and cost. Moreover, the efficient generation of light minimizes waste heat which needs to be managed and carried away which further reduces size, weight, and cost.

Ruggedness and elimination of alignment: The green laser light is generated within the chip, so external optical alignment is not required to maintain lasing. This dramatically reduces cost in the manufacturing process and also eliminates failure mechanisms for the use in the field.

Broad temperature operation: The GaN diode laser approach is not sensitive to minor changes in temperature. Therefore, requirements for several controls are eliminated including sensors for temperature and/or light, along with active temperature controls such as heaters or thermoelectric coolers. This greatly reduces the system complexity, cost, size, and weight, and eliminates failure mechanisms.

Elimination of the dangers of the residual 1064 nm beam: This GaN design produces only a green laser beam and does not produce a 1064 nm beam. This eliminates the blocking filter reducing cost, and eliminates the risk of emitting an extremely dangerous infrared beam.

Design flexibility in wavelength: By using the GaN approach, it is possible to achieve a slightly different wavelength such as 515 nm or 500 nm from the device. Such flexibility is important for dazzlers designed for dark environments, where the eye's sensitivity shifts and 500 nm is actually 20% brighter to the eye than light at 530 nm. Moreover, the flexible design enables one to fabricate a slightly different green wavelength which may be useful in preventing hostile parties from using 532 nm narrow band filter to avoid the effect of dazzling.

According to specific embodiments, green laser diodes (using nonpolar and/or semipolar GaN) for non lethal threat detection, threat assessment, threat de-escalation, visual warning technology, and laser dazzling are provided.

The present invention achieves these benefits and others in the context of known process technology. However, a further understanding of the nature and advantages of the present invention may be realized by reference to the latter portions of the specification and attached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified block diagram illustrating a laser dazzling device according to an embodiment of the present invention.

FIG. 1A is a simplified diagram illustrating an alternative laser dazzling device according to an embodiment of the present invention.

FIG. 2A is a detailed cross-sectional view of a laser device 200 fabricated on a {20-21} substrate according to an embodiment of the present invention.

FIG. 2B is a simplified diagram illustrating a cross-section of an active region with graded emission wavelength.

FIG. 2C is a simplified diagram illustrating a laser device with multiple active regions according embodiments of the present invention.

FIG. 3 is a simplified diagram of copackaged laser diodes mounted on a common surface within a single package.

DETAILED DESCRIPTION OF THE INVENTION

According to the present invention, techniques related to laser dazzling are provided. More specifically, embodiments of the present invention provide laser dazzling devices power by one or more green laser diodes characterized by a wavelength of about 500 nm to 540 nm. In various embodiments, laser dazzling devices according to the present invention include non-polar and/or semi-polar green laser diodes. In a specific embodiment, a single laser dazzling device includes a plurality of green laser diodes. There are other embodiments as well.

As described above, conventional laser devices are often inadequate for various reasons. More specifically, conventional DPPS laser devices are often inefficient. Although the three stage DPSS lasers do generate green laser light for the application today, several critical limitations of this design are noted below:

• • Inefficiency: Because each of the 3 processes is not perfectly efficient and has inherent loss, these green DPSS lasers are inefficient and therefore require powerful batteries to drive them, increasing the size, weight and cost. Moreover, the inefficient generation of light results in waste heat which needs to be managed and carried away which adds to the bulk and expense.
  • Fragility and sensitivity to alignment: In is absolutely critical to align each of the beams and crystals and optics with respect to one another in order to generate the green light. If misalignment occurs in assembly or in application, the green laser light generation will cease altogether. This adds cost in the manufacturing process and also presents failure mechanisms for the use in the field.
  • Temperature sensitivity: in order to achieve the 808 nm conversion to 1064 nm and the 1064 nm conversion to 532 nm, the temperature of the diode laser and/or crystals need to be precisely controlled. Minor changes in temperature beyond a few degrees C. can cause the green light generation process to decrease substantially or cease altogether. In order to overcome this, sensors for temperature and/or light, along with active temperature controls such as heaters or thermoelectric coolers are employed to maintain lasing in the green. These measures add to the systems cost, size, and weight, and present additional failure mechanisms.
  • Danger of the residual 1064 nm beam: This DPSS design produces a 1064 nm laser beam with power several times that of the green beam. While some of this light is converted to the green, residual 1064 nm laser light is inherent in the system since the frequency conversion process is not perfect. This residual infrared laser beam is typically blocked by the manufacturer using a filter which adds cost. If the filter were somehow to fail and the residual 1064 nm beam was emitted, the 1064 nm beam would be extremely dangerous because it is invisible to the human eye and may have enough power to cause blindness.
  • Fixed wavelength at 532 nm prevents flexible designs: Use of the DPSS approach results in a single wavelength output that is a property of the crystals used. It is not possible to achieve a slightly different wavelength such as 515 nm or 500 nm from the device unless another crystal would be invented. Such flexibility would be attractive since, in dark environments, the eye's sensitivity shifts and light at a wavelength of 500 nm is actually 20% brighter to the eye than light at 530 nm. Moreover, hostile parties may attempt to use narrow band filters to avoid the effect of dazzling, and using a slightly different green wavelength may be needed in the future.

In various embodiments, the present invention provide laser dazzling devices implemented using green laser diodes that directly produces green laser beams. More specifically, by utilizing a GaN diode laser that directly produces a green laser beam from a single stage design, one can efficiently produce a green beam from a tiny laser chip and eliminate or mitigate these drawbacks to existing DPSS systems in the field of laser dazzlers. According to the present invention, a green laser diode based on GaN technology would have the following advantages over existing DPSS approaches:

• • Efficiency: Because the GaN diode laser is a single stage, it is inherently more efficient and therefore requires less powerful batteries, decreasing the size, weight and cost. Moreover, the efficient generation of light minimizes waste heat which needs to be managed and carried away which further reduces size, weight, and cost.
  • Ruggedness and elimination of alignment: The green laser light is generated within the chip, so external optical alignment is not required to maintain lasing. This dramatically reduces cost in the manufacturing process and also eliminates failure mechanisms for the use in the field.
  • Broad temperature operation: The GaN diode laser approach is not sensitive to minor changes in temperature. Therefore, requirements for several controls are eliminated including sensors for temperature and/or light, along with active temperature controls such as heaters or thermoelectric coolers. This greatly reduces the system complexity, cost, size, and weight, and eliminates failure mechanisms.
  • Elimination of the dangers of the residual 1064 nm beam: This GaN design produces only a green laser beam and does not produce a 1064 nm beam. This eliminates the blocking filter reducing cost, and eliminates the risk of emitting an extremely dangerous infrared beam.
  • Design flexibility in wavelength: By using the GaN approach, it is possible to achieve a slightly different wavelength such as 515 nm or 500 nm from the device. Such flexibility is important for dazzlers designed for dark environments, where the eye's sensitivity shifts and 500 nm is actually 20% brighter to the eye than light at 530 nm. Moreover, the flexible design enables one to fabricate a slightly different green wavelength which may be useful in preventing hostile parties from using 532 nm narrow band filter to avoid the effect of dazzling.

FIG. 1 is a simplified block diagram illustrating a laser dazzling device according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown in FIG. 1, a laser dazzling device 100 includes a housing 101, a sight 102, a laser device 103, a driving circuit 104, a power source 105, an activation module 106, and an optical member 107. It is be appreciated that there can be other components as well.

The housing member 101 provides an enclosure for the components of the laser dazzling device. Depending on the specific application, the housing member 101 may be in various types of shapes. For example, the housing member 101 can be shaped like a pistol and includes a pistol grip. Alternative, the housing member 101 can be shaped like a rifle and comprises a rifle stock. Additionally, the housing member can be attached to a vehicle mount and/or include a tripod.

The laser device 103 according to embodiments of the present invention includes one or more laser diodes that directly emit a green laser beam without using frequency alteration (e.g., frequency double or DPSS) techniques. In a specific embodiment, the laser device includes a green laser diode that includes an active region and a cavity member. The green laser diode is configured to emit a laser beam having a wavelength about 500 nm to 540 nm. In a specific embodiment, the wavelength is about 532 nm. The active region of the green laser diode includes gallium nitride material. For example, the green laser diode includes a mirror surface where the laser beam is emitted, and the laser beam is characterized by a first direction. Depending on the application, the green laser diode can be associated with one or more operational modes. For example, each of the operational modes is associated with a operating frequency.

In one embodiment, the laser device 103 comprises a plurality of green laser diodes sharing a single substrate. For example, the green laser diodes are monolithically integrated during the manufacturing process of the green laser diode, as is described below. By using a plurality of green laser diodes, the power level of the laser dazzling device can be increased. For example, a high power laser device having a plurality of green laser diodes is used for high-power military laser dazzling systems wherein the laser beams are used to disable weapons sensors. Alternatively, the laser device 103 comprises a plurality of green laser diodes sharing a single package.

According to various embodiments of the present invention, the green laser diode can be semi-polar or non-polar. For example, green laser diodes are fabricated from a bulk substrate. Since the green laser diodes directly emit laser beams in green wavelength range, the laser dazzling device is free from a frequency doubling crystal.

In many instances, the output power level of laser dazzling device needs to be limited to avoid permanent injury to eyes. In a specific embodiment, the laser beam is characterized by an energy level of less than 500 mW.

The driving circuit 104 is electrically coupled to the laser device 103. Among other things, the driving circuit 104 is specifically adapted to deliver electrical energy to the laser device. For example, the electrical energy can less than 800 mW. The driving circuit 104 may deliver electrical energy to the laser device 103 in various ways. In one embodiment, the driving circuit is adapted to deliver electrical energy to the laser device in pulses.

The power source 105 is electrically coupled to the driving circuit. For example, the power source comprises a battery. The battery may be rechargeable or disposable. For example, NiMH or LiON rechargeable battery is used for the power source.

The activation module 106 is electrically coupled to the driving circuit. The activation module is configured to send an activation signal to the driving circuit. For example, an operator is able to cause the driving circuit to provide electrical energy to the laser device, which in response emits a laser beam. In one embodiment, the activation module is configured like a traditional trigger unit, which includes a trigger and a safety.

The sight 102 is provided for aligning the laser beam to a desired position. Depending on the application, the sight can be an open sight, an aperture sight, a red dot sight, a hologram sight, and/or a scope.

The optical member 107 is used to focus the laser beam. In an embodiment, the optical member 107 is positioned within a vicinity of the emitting portion of the laser device. For example, the optical member 107 includes a collimation lens and telescope to collimate and size the laser beam. In one embodiment, the optical member 107 includes an optical concentrator aligned with the laser device. In another embodiment, the optical member comprises a waveguide for projecting the laser beam along the first direction.

As mentioned above, various components of the laser dazzling device 100 may be added, removed, modified, and/or replaced. FIG. 1A is a simplified diagram illustrating an alternative laser dazzling device according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives.

As mentioned above, the laser dazzling devices according to the present invention utilize green laser diodes. FIG. 2A is a detailed cross-sectional view of a laser device 200 fabricated on a {20-21} substrate according to an embodiment of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. As shown, the laser device includes gallium nitride substrate 203, which has an underlying n-type metal back contact region 201. In a specific embodiment, the metal back contact region is made of a suitable material such as those noted below and others. Further details of the contact region can be found throughout the present specification and more particularly below.

In a specific embodiment, the device also has an overlying n-type gallium nitride layer 205, an active region 207, and an overlying p-type gallium nitride layer structured as a laser stripe region 211. In a specific embodiment, each of these regions is formed using at least an epitaxial deposition technique of metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or other epitaxial growth techniques suitable for GaN growth. In a specific embodiment, the epitaxial layer is a high quality epitaxial layer overlying the n-type gallium nitride layer. In some embodiments the high quality layer is doped, for example, with Si or O to form n-type material, with a dopant concentration between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³.

In a specific embodiment, an n-type Al_uIn_vGa_1-u-vN layer, where 0≦u, v, u+v≦1, is deposited on the substrate. In a specific embodiment, the carrier concentration may lie in the range between about 10¹⁶ cm⁻³ and 10²⁰ cm⁻³. The deposition may be performed using metalorganic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE). Of course, there can be other variations, modifications, and alternatives.

As an example, the bulk GaN substrate is placed on a susceptor in an MOCVD reactor. After closing, evacuating, and back-filling the reactor (or using a load lock configuration) to atmospheric pressure, the susceptor is heated to a temperature between about 1000 and about 1200 degrees Celsius in the presence of a nitrogen-containing gas. In one specific embodiment, the susceptor is heated to approximately 1100 degrees Celsius under a flow of ammonia. A flow of a gallium-containing metalorganic precursor, such as trimethylgallium (TMG) or triethylgallium (TEG) is initiated, in a carrier gas, at a total rate between approximately 1 and 50 standard cubic centimeters per minute (sccm). The carrier gas may comprise hydrogen, helium, nitrogen, or argon. The ratio of the flow rate of the group V precursor (ammonia) to that of the group III precursor (trimethylgallium, triethylgallium, trimethylindium, trimethylaluminum) during growth is between about 2000 and about 12000. A flow of disilane in a carrier gas, with a total flow rate of between about 0.1 and 10 sccm, is initiated.

In a specific embodiment, the laser stripe region is made of the p-type gallium nitride layer 211. In a specific embodiment, the laser stripe is provided by an etching process selected from dry etching or wet etching. In a preferred embodiment, the etching process is dry, but can be others. As an example, the dry etching process is an inductively coupled process using chlorine bearing species or a reactive ion etching process using similar chemistries. Again as an example, the chlorine bearing species are commonly derived from chlorine gas or the like. The device also has an overlying dielectric region, which exposes contact region 213. In a specific embodiment, the dielectric region is an oxide such as silicon dioxide or silicon nitride, but can be others. The contact region is coupled to an overlying metal layer 215. The overlying metal layer is a multilayered structure containing gold and platinum (Pt/Au), nickel gold (Ni/Au), but can be others. Of course, there can be other variations, modifications, and alternatives.

In a specific embodiment, the laser device has active region 207. The active region can include one to twenty quantum well regions according to one or more embodiments. As an example, following deposition of the n-type Al_uIn_vGa_1-u-vN layer for a predetermined period of time, so as to achieve a predetermined thickness, an active layer is deposited. The active layer may be comprised of multiple quantum wells, with 2-10 quantum wells. The quantum wells may be comprised of InGaN with GaN barrier layers separating them. In other embodiments, the well layers and barrier layers comprise Al_wIn_xGa_1-w-xN and Al_yIn_zGa_1-y-zN, respectively, where 0≦w, x, y, z, w+x, y+z≦1, where w<u, y and/or x>v, z so that the bandgap of the well layer(s) is less than that of the barrier layer(s) and the n-type layer. The well layers and barrier layers may each have a thickness between about 1 nm and about 20 nm. The composition and structure of the active layer are chosen to provide light emission at a preselected wavelength. The active layer may be left undoped (or unintentionally doped) or may be doped n-type or p-type. Of course, there can be other variations, modifications, and alternatives.

In a specific embodiment, the active region can also include an electron blocking region, and a separate confinement heterostructure. In some embodiments, an electron blocking layer is preferably deposited. The electron-blocking layer may comprise Al_sIn_tGa_1-s-tN, where 0≦s, t, s+t≦1, with a higher bandgap than the active layer, and may be doped p-type. In one specific embodiment, the electron blocking layer comprises AlGaN. In another embodiment, the electron blocking layer comprises an AlGaN/GaN super-lattice structure, comprising alternating layers of AlGaN and GaN, each with a thickness between about 0.2 nm and about 5 nm. Of course, there can be other variations, modifications, and alternatives.

As noted, the p-type gallium nitride structure is deposited above the electron blocking layer and active layer(s). The p-type layer may be doped with Mg, to a level between about 10¹⁶ cm⁻³ and 10²² cm⁻³, and may have a thickness between about 5 nm and about 1000 nm. The outermost 1-50 nm of the p-type layer may be doped more heavily than the rest of the layer, so as to enable an improved electrical contact. In a specific embodiment, the laser stripe is provided by an etching process selected from dry etching or wet etching. In a preferred embodiment, the etching process is dry, but can be others. The device also has an overlying dielectric region, which exposes contact region 213. In a specific embodiment, the dielectric region is an oxide such as silicon dioxide, but can be others. Of course, there can be other variations, modifications, and alternatives.

According to an embodiment, the as-grown material gain peak is varied spatially across a wafer. As a result, different wavelength and/or color can be obtained from one fabricated laser to the next laser on the same wafer. The as-grown gain peak wavelength can be shifted using various methods according to embodiments of the present invention. According to one embodiment, the present invention utilizes growth non-uniformities where the as-grown material has an emission wavelength gradient. For example, the growth non-uniformity can be obtained as a result of temperature and/or growth rate gradients in the light emitting layers in the epitaxial growth chamber. For example, such wavelength gradients can be intentional or non-intentional, and the differences in wavelengths range from 10 to 40 nm deviation. For example, this method enables multiple lasers on the same chip to operate at different wavelengths.

In a specific embodiment, an optical device configured to provide laser beams at different wavelengths is provided. The device includes a gallium and nitrogen containing substrate including a first crystalline surface region orientation. For example, the substrate member may have a surface region on the polar plane (c-plane), nonpolar plane (m-plane, a-plane), and semipolar plain ({11-22}, {10-1-1}, {20-21}, {30-31}). The device also includes an active region comprising a barrier layer and a light emission layer, the light emission layer being characterized by a graduated profile associated with a peak emission wavelength gradient, the peak emission wavelength gradient having a deviation of at least 10 nm. Also, the device includes a first cavity member overlaying a first portion of the emission layer, the first portion of the emission layer being associated with a first wavelength, the first cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the first cavity member being adapted to emit a first laser beam at the first wavelength. The device further includes a second cavity member overlaying a second portion of the emission layer, the second portion of the emission layer being associated with a second wavelength, a difference between the first and second wavelengths being at least 50 nm, the second cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the second cavity member being adapted to emit a second laser beam at a second wavelength. Additionally, the device includes an output region wherein the first laser beam and the second laser beam are combined.

As mentioned above, a laser dazzling device may include multiple green laser diodes for various purposes, such as increased power level, varying wavelength, and others. FIG. 2B is a simplified diagram illustrating a cross-section of an active region with graded emission wavelength. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications.

In certain embodiments of the present invention, multiple laser wavelengths are obtained by manipulating the as-grown gain peak through selective area epitaxy (SAE), where dielectric patterns are used to define the growth area and modify the composition of the light emitting layers. Among other things, such modification of the composition can be used to cause different gain peak wavelengths and hence different lasing wavelengths. For example, by using SAE processes, a device designer can have a high degree of spatial control and can safely achieve 10-30 nm, and sometimes even more, of wavelength variation over the lasers. For example, the SAE process is described in a U.S. patent application Ser. No. 12/484,924, filed Jun. 15, 2009, entitled “SELECTIVE AREA EPITAXY GROWTH METHOD AND STRUCTURE FOR MULTI-COLOR DEVICES”. For example, this method enables multiple lasers on the same chip to operate at different wavelengths.

In a specific embodiment, a laser apparatus manufactured using SAE process with multiple wavelengths and/or color is provided. The laser apparatus includes a gallium and nitrogen containing substrate including a first crystalline surface region orientation. The apparatus also includes an active region comprising a barrier layer and a plurality of light emission layers, the plurality of light emission layers including a first emission layer and a second emission layer, the first emission layer being characterized by a first wavelength, the second emission layer being characterized by a second wavelength, a difference between the first wavelength and the second wavelength is at least 10 nm. For example, the first and second emission layers are formed using selective area epitaxy processes.

The apparatus includes a first cavity member overlaying the first emission layer, the first cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the first cavity member being adapted to emit a first laser beam at the first wavelength. The apparatus also includes a second cavity member overlaying the second the emission layer, the second cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um the second cavity member being adapted to emit a second laser beam at the second wavelength. The apparatus additionally includes an output region wherein the first laser beam and the second laser beam are combined.

As explained above, it is often desirable to combine the first and second wavelengths or colors associated thereof for various applications. For example, the apparatus may have optics having dichroic coatings for combining the first and the second laser beam. In one embodiment, the apparatus includes a plurality of polarizing optics for combining the first and the second laser beam. In a specific embodiment, the first cavity member and the second cavity member share a common cleaved facet of mirror edges, which is configured to combine the first and second laser beams.

The first and second laser beams can be associated with a number of color combinations. For example, the first wavelength is associated with a green color and the second wavelength is associated with a blue color.

It is to be appreciated that the laser apparatus can be implemented on various types of substrates. For example, the first crystalline surface region orientation can be a {20-21} plane, and first crystalline surface region orientation can also be a {30-31} plane.

The laser apparatus may also include other structures, such as a surface ridge architecture, a buried hetereostructure architecture, and/or a plurality of metal electrodes for selectively exciting the active region For example, the active region comprises a first and second gallium and nitrogen containing cladding layers and an indium and gallium containing emitting layer positioned between the first and second cladding layers. The laser apparatus may further includes an n-type gallium and nitrogen containing material and an n-type cladding material overlying the n-type gallium and nitrogen containing material.

In certain embodiments of the present invention, multiple laser wavelengths and/or colors are obtained by providing multiple active regions, and each of the active regions is associated with a specific wavelength (or color). More specifically, multiple growth of active regions is performed across a single chip. In this technique a wafer is loaded in a growth chamber for the growth of an active region with one gain peak. After this growth, the wafer is subjected to one or more lithography and processing steps to remove a portion of the active region in some areas of the wafer. The wafer would then be subjected to a second growth where a second active region with a second peak gain wavelength is grown. Depending on the specific need, the processes of growing and removing active regions can be repeated many times. Eventually, this may be followed by the fabrication of laser diodes strategically positioned relative to these different active regions to enable lasing at various wavelengths.

FIG. 2C is a simplified diagram illustrating a laser device with multiple active regions according embodiments of the present invention. This diagram is merely an example, which should not unduly limit the scope of the claims. One of ordinary skill in the art would recognize many variations, alternatives, and modifications. As an example, each active region is used to emit a green laser beam.

According to an embodiment, the following steps are performed in a method for forming a device that includes laser devices having multiple active regions:

• • 1. providing a gallium and nitrogen containing substrate including a first crystalline surface region orientation;
  • 2. defining a first active region by performing a selective etching process;
  • 3. forming a barrier layer within the first active region;
  • 4. growing a first emission layer within the first active region, the first emission layer being characterized by a first wavelength;
  • 5. defining a second active region by performing a selective etching process;
  • 6. growing a second emission layer within the second active area, the second emission layer being characterized by a second wavelength, a difference between the first gain peak wavelength and the second gain peak wavelength being at least 10 nm;
  • 7. forming a first cavity member overlaying the first emission layer, the first cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the first cavity member being adapted to emit a first laser beam at the first wavelength;
  • 8. forming a second cavity member overlaying the second the emission layer, the second cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um the second cavity member being adapted to emit a second laser beam at the second wavelength; and
  • 9. aligning the first and second cavity members to combine the first and second laser beams at a predetermine region

Depending on the application, the above method may also include other steps. For example, the method may include providing an optical member for combining the first and second laser beams. In one embodiment, the method includes shaping a first cleaved surface of the first cavity member, shaping a second cleaved surface of the second cavity member, and aligning the first and second cleaved surfaces to cause the first and second laser beams to combine.

It is to be appreciated that the method described above can be implemented using various types of substrates. As explained above, the substrate member may have a surface region on the polar plane (c-plane), nonpolar plane (m-plane, a-plane), and semipolar plain ({11-22}, {10-1-1}, {20-21}, {30-31}). In the method described above, two active regions and two cavity members are formed. For example, each active region and cavity member pair is associated with a specific wavelength. Depending on the application, additional active regions and cavity members may be formed to obtain desired wavelengths and/or spectral width. In a preferred embodiment, each of the active regions is characterized by a specific spatial dimension associated with a specific wavelength.

In a specific embodiment, a laser apparatus having multiple active regions that provide multiple wavelengths and/or colors is described. The laser apparatus includes a gallium and nitrogen containing substrate including a first crystalline surface region orientation. In a specific embodiment, the substrate comprises Indium bearing material. The apparatus also includes a first active region comprising a barrier layer and a first emission layer, the first emission layer being characterized by a first gain peak wavelength. The apparatus includes a second active region comprising a second emission layer, the second emission layer being characterized by a second gain peak wavelength, a difference between the first gain peak wavelength and the second gain peak wave length is at least 10 nm.

The apparatus further includes a first cavity member overlaying the first emission layer, the first cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the first cavity member being adapted to emit a first laser beam at the first wavelength. The apparatus additionally includes a second cavity member overlaying the second emission layer, the second cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the second cavity member being adapted to emit a second laser beam at the second wavelength. The apparatus further includes an output region wherein the first laser beam and the second laser beam are combined.

As explained above, it is often desirable to combine the first and second wavelengths or colors associated thereof for various applications. For example, the apparatus may have optics having dichroic coatings for combining the first and the second laser beam. In one embodiment, the apparatus includes a plurality of polarizing optics for combining the first and the second laser beam. In a specific embodiment, the first cavity member and the second cavity member share a common cleaved facet of mirror edges, which is configured to combine the first and second laser beams.

The first and second laser beams can be associated with a number of color combinations. For example, the first wavelength is associated with a green color and the second wavelength is associated with a blue color.

It is to be appreciated that the laser apparatus can be implemented on various types of substrates. For example, the first crystalline surface region orientation can be a {20-21} plane, and first crystalline surface region orientation can also be a {30-31} plane.

The laser apparatus may also include other structures, such as a surface ridge architecture, a buried hetereostructure architecture, and/or a plurality of metal electrodes for selectively exciting the active region. For example, the active region comprises first and second gallium and nitrogen containing cladding layers and an indium and gallium containing emitting layer positioned between the first and second cladding layers. The laser apparatus may further includes an n-type gallium and nitrogen containing material and an n-type cladding material overlying the n-type gallium and nitrogen containing material.

It is to be appreciated that embodiments of the present invention provide methods for obtaining multiple laser wavelengths and/or colors after the active regions have already been formed. More specifically, the gain-peak of the semiconductor material can be spatially manipulated post-growth through quantum well intermixing (QWI) processes and/or disordering of the light emitting layers. A QWI process makes use of the metastable nature of the compositional gradient found at heterointerfaces. The natural tendency for materials to interdiffuse is the basis for the intermixing process. Since the lower energy light emitting quantum well layers are surrounded by higher energy barriers of a different material composition, the interdiffusion of the well-barrier constituent atoms will result in higher energy light emitting layers and therefore a blue-shifted (or shorter) gain peak.

The rate at which this process takes place can be enhanced with the introduction of a catalyst. Using a lithographically definable catalyst patterning process, the QWI process can be made selective. This is the process by which virtually all selective QWI is performed, whether it is by the introduction of impurities or by the creation of vacancies. There are a great number of techniques that have evolved over the years to accomplish selective intermixing, such as impurity-induced disordering (IID), impurity-free vacancy-enhanced disordering (IFVD), photoabsorption-induced disordering (PAID), and implantation-enhanced interdiffusion to name just a few. Such methods are capable of shifting the peak gain wavelengths by 1 to over 100 nm. By employing one of these mentioned methods or any other QWI method to detune the gain peak of adjacent laser devices, the convolved lasing spectrum of the side by side devices can be altered.

In one embodiment, a laser apparatus capable of multiple wavelengths is manufactured by using one of the QWI processes described above. The apparatus includes a gallium and nitrogen containing substrate including a first crystalline surface region orientation. The apparatus also includes an active region comprising a barrier layer and a plurality of light emission layers, the plurality of light emission layers including a first emission layer and a second emission layer, the barrier layer being characterized by a first energy level, the first emission layer being characterized by a first wavelength and a second energy level, the second energy level being lower than the first energy level, the first emission layer having a first amount of material diffused from the barrier layer, the second emission layer being characterized by a second wavelength, a difference between the first gain peak wavelength and the second gain peak wavelength being at least 10 nm. For example, the second emission layer has a second amount of material diffused from the barrier layer.

The apparatus also includes a first cavity member overlaying the first emission layer, the first cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um, the first cavity member being adapted to emit a first laser beam at the first wavelength. The apparatus includes a second cavity member overlaying the second emission layer, the second cavity member being characterized by a length of at least 100 um and a width of at least 0.5 um the second cavity member being adapted to emit a second laser beam at the second wavelength. The apparatus includes an output region wherein the first laser beam and the second laser beam are combined.

Depending on the application, the active region may include various types of material, such as InP material, GaAs material, and others. The apparatus may have optics having dichroic coatings for combining the first and the second laser beams. In one embodiment, the apparatus includes a plurality of polarizing optics for combining the first and the second laser beams. In a specific embodiment, the first cavity member and the second cavity member share a common cleaved facet of mirror edges, which is configured to combine the first and second laser beams. The first and second laser beams are both green but in slightly different wavelengths.

It is to be appreciated that the laser apparatus can be implemented on various types of substrates. For example, the first crystalline surface region orientation can be a {20-21} plane, and first crystalline surface region orientation can also be a {30-31} plane. The laser apparatus may also include other structures, such as a surface ridge architecture, a buried hetereostructure architecture, and/or a plurality of metal electrodes for selectively exciting the active region For example, the active region comprises first and second gallium and nitrogen containing cladding layers and an indium and gallium containing emitting layer positioned between the first and second cladding layers. The laser apparatus may further includes an n-type gallium and nitrogen containing material and an n-type cladding material overlying the n-type gallium and nitrogen containing material.

In various embodiments, laser diodes formed on different substrates are packaged together. It is to be appreciated that by sharing packaging of laser diodes, it is possible to produce small device applications (e.g., pico projectors), as multiple laser diodes can tightly fit together. For example, light engines having laser diodes in multiple colors are typically capable of reducing the amount of speckles in display applications. In addition, co-packaged laser diodes are often cost-efficient, as typically fewer optics are needed to combined laser beam outputs from laser diodes as a result of sharing packages.

FIG. 3 is a simplified diagram of copackaged laser diodes mounted on a common surface within a single package. This diagram is merely an example, which should not unduly limit the scope of the claims herein. One of ordinary skill in the art would recognize other variations, modifications, and alternatives. For example, both laser 1 and laser 2 are green laser diodes. By combining the output from both laser diodes, a combined laser beam with high power output can be achieved.

While the above is a full description of the specific embodiments, various modifications, alternative constructions and equivalents may be used. Therefore, the above description and illustrations should not be taken as limiting the scope of the present invention, which is defined by the appended claims.