Surface-emitting laser device

Abstract

A surface-emitting laser device and a method for manufacturing and operating the same are disclosed. The surface-emitting laser device comprises an active layer, a semiconductor layer optically coupled to the active layer, and a photonic crystal structure disposed within the semiconductor layer. The device further comprises a laser region and a detector region. The laser region includes a first set of electrical contacts located on opposite sides of the active layer and the semiconductor layer, and generates the output field of the device. The detector region includes a second set of electrical contacts located on opposite sides of the active layer and the semiconductor layer, and located outside the first laser region. The detector region is configured to generate an output current proportional to the output field. The presence of the detector region within the device improves the structure and power monitoring techniques compared to the prior art.

Description

Technical Field

[0001] The present invention relates to the field of surface emitting laser devices and methods for manufacturing and operating such devices. In particular, the present invention relates to photonic crystal surface emitting laser (PCSEL) devices.

Background Art

[0002] Semiconductor laser devices are solid-state lasers based on a semiconductor gain medium, and optical amplification is typically achieved by the induced recombination of charge carriers. Most semiconductor laser devices are laser diodes based on a semiconductor gain medium, and are excited by an electric current in a region where an n-type doped semiconductor material and a p-type doped semiconductor material are in contact. Since the photon energy of a laser diode is close to the bandgap energy, different emission wavelengths can be realized by using different compositions of bandgap energy.

[0003] There are a variety of semiconductor laser devices, covering a wide parameter range and diverse application fields. The Fabry-Perot (FP) laser is a basic technology as a semiconductor laser device. In those devices, both the laser feedback and emission are in-plane, the gain reflection is generated by facet mirrors, and the generated output light is emitted from the end face of the laser. Therefore, the FP laser is also called an edge-emitting laser (EEL).

[0004] As another type of EEL, there is a distributed feedback (DFB) laser. DFB lasers also have in-plane feedback and emission, but in those devices, the gain reflection is generated by using a grating structure.

[0005] Another known type of semiconductor laser device technology is the vertical-cavity surface-emitting laser (VCSEL). The laser resonator of a VCSEL consists of two distributed Bragg reflection (DBR) mirrors with an active region positioned between DBR mirrors. In a VCSEL, both laser feedback and emission are out-of-plane, and the laser output light is emitted from the top surface of the laser.

[0006] Photonic crystal surface-emitting lasers (PCSELs) represent a newer class of semiconductor laser devices. PCSELs have been found to possess desirable properties such as coherent oscillation and a low divergence angle of the emitted light. Furthermore, PCSELs are the only semiconductor laser design that employs both in-plane feedback and out-of-plane, surface emission.

[0007] PCSELs can be fabricated from various semiconductor materials. Figure 1 shows a simplified PCSEL structure, indicated by reference numeral 1. Specifically, Figure 1(a) shows an exploded perspective view of PCSEL1, and Figure 1(b) shows a cross-sectional view of PCSEL1.

[0008] It can be seen that PCSEL1 has a semiconductor substrate 2 on which other layers of PCSEL1 are formed. The semiconductor substrate 2 is usually made of n-type semiconductor material, but alternatively, it can also be made of p-type semiconductor material.

[0009] As shown in Figure 1, the other layers of PCSEL1 are the lower cladding layer 3, the active layer 4, the photonic crystal layer 5, and the upper cladding layer 6. As will be understood by those skilled in the art, it is also possible to include one or more additional intermediate layers within PCSEL1 as needed.

[0010] The purpose of the lower cladding layer 3 and the upper cladding layer 6 is to confine the light generated in the active layer 4. The lower cladding layer 3 and the upper cladding layer 6 may consist of first and second gradient cladding layers, and it has been found that incorporating gradient cladding layers improves electrical conductivity through the PCSEL 1 and improves the light confinement performance within the active layer 4.

[0011] The active layer 4 of a PCSEL can contain quantum wells or quantum dots. For example, the active layer can contain one or more of the following: InGaAs / GaAs quantum wells, InAs / GaAs quantum dots, GaAs / AlGaAs quantum wells, InGaAsP quantum wells, and AlInGaAsP quantum wells, but there are many other active layer designs known to those skilled in the art.

[0012] The photonic crystal layer 5 contains a semiconductor material such as InGaP. However, the photonic crystal layer 5 may also contain alternative materials such as InGaAsP or other suitable semiconductor materials. The photonic crystal layer 5 is formed by patterning periodic regions 7 having a second refractive index different from the first refractive index of the semiconductor material, thereby creating a periodic lattice structure within the photonic crystal layer 5. The periodic regions 7 having a second refractive index different from that of the semiconductor material may be formed by voids or holes. Alternatively, the periodic regions 7 can also be filled by upward growth with a suitable filler material having a second refractive index (e.g., GaAs). The lattice structure of the photonic crystal layer 5 causes Bragg diffraction within the photonic crystal layer 5, thereby causing light to resonate within the photonic crystal layer 5 at a specific wavelength determined by the periodicity or lattice constant of the photonic crystal layer 5.

[0013] The electrical contacts 8a and 8b are located on the outer surface of the PCSEL1. The first electrical contact 8a is located on the output surface 9 of the PCSEL1, and the second electrical contact 8b is provided adjacent to the lower cladding layer 3.

[0014] With the structure described above, when current is supplied between the first and second electrical contacts 8a and 8b, the PCSEL1 oscillates and the output field 10 is radiated from the output surface 9.

[0015] As shown in Figure 1, the first electrical contact 8a is square and has an aperture 11 from which the output light 10 of the PCSEL1 is extracted when the PCSEL1 is oscillating. However, as will be understood by those skilled in the art, the first electrical contact 8a may be any suitable shape including a central aperture from which the output field 10 can be emitted.

[0016] In the aforementioned types of semiconductor lasers (EEL, VCSEL, and PCSEL), power monitoring of the output field is essential in applications where precise control of the laser's output power is required, such as in optical communication systems. Furthermore, power monitoring of laser devices is useful for ensuring that the laser is operating safely and efficiently, and for preventing device damage or failure.

[0017] By continuously monitoring a portion of the output field with a suitable photodetector, it is possible to detect fluctuations in the laser's output power caused by various factors, such as temperature variations, device aging, or changes in input voltage and current. The photodetector converts optical power into an electric current, which can then be measured by an external circuit to determine the output power. Generally, to compensate for fluctuations in the measured output power, appropriate closed-loop power control can be used to maintain the output power at a constant level.

[0018] In EELs, power monitoring of the output light is generally achieved by placing an external photodetector on the back facet of the device. While the majority of the output power is emitted from the front facet of the EEL, a small portion of the light ultimately leaks out through the back facet. The amount of light leakage from the back facet of the EEL is proportional to the amount of light emitted from the front facet. Therefore, by monitoring the power emitted from the back facet of the EEL, output power fluctuations can be compensated for using an appropriate power control loop.

[0019] Unlike EELs, VCSELs do not have in-plane feedback or emission. Therefore, VCSELs employ alternative methods for power monitoring of the output beam. Typically, a portion of the light emitted by the VCSEL from the top surface of the laser is branched from the main output beam and guided to a photodetector. This method requires additional external optical elements to properly align the branched beam to the photodetector after branching a portion of the output field.

[0020] As described above, the design of PCSEL1 allows for both in-plane feedback and out-of-plane and surface emission (a portion of its output can be extracted for monitoring). Therefore, any of the power monitoring methods described above can be employed with PCSEL1. In particular, as shown in Figure 1, by placing a photodetector 12 at one end of PCSEL1, light leakage from a portion of the light traveling in the in-plane direction within the photonic crystal layer 5 can be collected by the photodetector 12. Thus, fluctuations in output power can similarly be compensated for by using an appropriate power control loop 13. Alternatively, a portion of the output light 10 can be extracted from the main output beam and used for monitoring.

[0021] When using the above method to monitor the output power of a laser device, several known drawbacks exist.

[0022] Firstly, accurate power measurement requires careful alignment of the extracted light and calibration of the power monitoring device 12. However, the alignment of the light guided to the power monitoring device 12 can drift over time. As a result, the user of the laser system will need to periodically realign the beam to the power monitoring device 12. Failure to realign the beam will result in inaccurate power measurements due to beam misalignment, leading to a decrease in the overall performance of the laser system. This can be undesirable, especially in various applications where ease of use is important.

[0023] Furthermore, additional optical systems required for extraction and alignment can lead to undesirable power losses, reducing the overall available output power of the laser system.

[0024] Another drawback of the power monitoring device 12 described above is that it can introduce extra noise into the semiconductor laser system. This extra noise can also have a significant impact on the accuracy of power measurement.

[0025] Also, in applications where miniaturization of the semiconductor laser is essential, the power monitoring methods described above are not ideal. This is because the photodetector 12 and the additional optical system increase the overall footprint of the semiconductor laser.

[0026] Therefore, generally, there is a need for devices and / or methods to address one or more of the above-mentioned problems. SUMMARY OF THE INVENTION

[0027] One of the objects and aims of the present invention is to provide an alternative surface-emitting laser device that avoids or reduces one or more drawbacks or disadvantages of the prior art.

[0028] In particular, one of the objects of one aspect of the present invention is to provide a surface-emitting laser device (which may be a PCSEL device) with improved structure and power monitoring method compared to the prior art.

[0029] According to a first aspect of the present invention, there is provided a surface-emitting laser device, the surface-emitting laser device comprising an active layer, a semiconductor layer optically coupled to the active layer, a first photonic crystal structure including an array of scattering centers disposed within the semiconductor layer, a first laser region defined by a first set of electrical contacts disposed on opposite sides of the coupled active layer and semiconductor layer and configured to generate a first output field of the surface-emitting laser device Outside the first laser region, there is provided a first detector region defined by a set of second electrical contacts disposed on opposite sides of the combined active layer and semiconductor layer, and configured to generate a first output current proportional to the first output field.

[0030] Separate electrical contacts defining the first laser region and the first detector region enable a drive current to be applied to the first laser region, and the first detector region outputs a detection current proportional to or at least related to the output power from the first laser region.

[0031] Thus, in the surface-emitting laser device, an integrated detector region is provided by utilizing the specific semiconductor structure of the device, particularly the feature that the output field is perpendicular to the gain. The presence of the integrated detector region eliminates the need for external optical elements and photodetectors for power monitoring. This enables the realization of a surface-emitting laser device smaller than similar devices known in the prior art. Furthermore, the integrated detector region eliminates the need for continuous alignment of the photodetector, which is a common problem with external photodetectors, thus improving the continuous power monitoring of the surface-emitting laser. Additionally, the use of the integrated detector region removes noise elements specific to external photodetectors, thereby enhancing the accuracy of the surface-emitting laser device and reducing the overall noise level.

[0032] Preferably, the first photonic crystal structure is configured to provide an in-plane optical field within the semiconductor layer.

[0033] Preferably, the first detector region is configured to detect the in-plane optical field generated by the photonic crystal structure.

[0034] Most preferably, the first detector region operates in reverse bias.

[0035] Preferably, the first detector region provides feedback to the control loop, which adjusts the output power of the first output field by compensating for fluctuations in the detected power of the in-plane optical field. Adjusting the output power of the first output field may include maintaining the output power at a constant level. Constant output power is important for many commercial applications, and by employing a suitable control loop, the user can reduce the input required to maintain constant power.

[0036] Optionally, the surface-emitting laser device further includes two or more laser regions, each characterized by a set of electrical contacts, and each laser region is configured to generate a distinct output field for the surface-emitting laser device.

[0037] Preferably, the first detector region is configured to detect the in-plane optical field generated within each laser region.

[0038] Preferably, the control loop is configured to selectively operate one of two or more laser regions to generate a single output field.

[0039] Preferably, the control loop is configured to automatically switch to selectively operating one of the remaining laser regions when the currently selected laser region no longer generates the required output power.

[0040] Since the output power from each laser region is monitored by the same integrated detector region, the output field from the currently selected laser region can be set to the same constant output power as the previously selected output field. Each laser region has its own lifetime, and at the end of its lifetime, it can no longer generate the required output power. By switching to another laser region that generates the same output power as the previously selected laser region, the device's lifespan is extended. Furthermore, since there is no device downtime when switching between different output fields, this can be important in a variety of applications.

[0041] Preferably, the surface-emitting laser device further comprises an output coupler.

[0042] Preferably, two or more laser regions are configured to guide the associated output fields to the output coupler.

[0043] Preferably, the direction of the output fields from one or more laser regions is controlled by modulating the photonic crystal structure using a modulation pattern. The photonic crystal structure can also be modulated by applying a voltage to the photonic crystal. By modulating the photonic crystal structure, two output fields (rather than a single output field) are generated from each photonic crystal.

[0044] Alternatively, the direction of the output field can be adjusted by changing the size, shape, and / or orientation of the scattering centers in the photonic crystal structure.

[0045] Alternatively, the surface-emitting laser device may further include a beam steering optical system configured to adjust the direction of the output field. Optionally, the beam steering optical system may include a micro-electromechanical system mirror or a diffraction grating.

[0046] Optionally, the surface-emitting laser device further comprises two or more integrated detector regions, each integrated detector region characterized by a set of electrical contacts, and each of the two or more integrated detector regions is configured to generate an output current proportional to one or more output fields.

[0047] Preferably, each integrated detector region is configured to detect an in-plane optical field generated within two or more laser regions.

[0048] Preferably, the active layer includes a multiple quantum well active layer.

[0049] Preferably, the scattering centers consist of vacancies (commonly called atoms in this art) formed within the semiconductor layer. Most preferably, the vacancies are filled with a second n-type semiconductor material. Optionally, the second n-type semiconductor material comprises indium phosphide (InP) and a dopant material of tin, sulfur, or indium.

[0050] Preferably, the surface-emitting laser device further includes a substrate on which each layer of the surface-emitting laser is formed.

[0051] Preferably, the surface-emitting laser device comprises a p-type semiconductor layer disposed between the active layer and the semiconductor substrate, and an n-type semiconductor layer disposed on the opposite side of the active layer from the p-type semiconductor layer.

[0052] Optionally, the surface-emitting laser device comprises an n-type semiconductor layer disposed between the active layer and the semiconductor substrate, and a p-type semiconductor layer disposed on the opposite side of the active layer from the n-type semiconductor layer.

[0053] Advantageously, the above-described embodiment of the structure makes it possible to extend the lifespan of the surface-emitting laser device. The first output field is monitored by an integrated detector region, and so the integrated detector region detects when the power of the first output field begins to decrease due to the limited lifespan of the semiconductor structure. Therefore, the surface-emitting laser device can be configured to shut off the first output field when it approaches the end of its lifespan and instead generate a second output field from a second laser region. By using an appropriate control loop, the output power from the second output field can be fixed to the same power as the first output field. In this way, a surface-emitting laser device with an extended lifespan can be manufactured.

[0054] Optionally, one or more wavelength-selective reflectors can be placed outside the semiconductor layer containing the photonic crystal structure. The presence of one or more reflectors can reduce the effects of undesirable light leakage from the semiconductor layer.

[0055] Most preferably, the electrical contacts associated with the laser region (or each laser region) include an aperture that defines the output surface of the surface-emitting laser device.

[0056] In one embodiment, the surface-emitting laser device comprises two laser regions and a detector region positioned between them. In another embodiment, the surface-emitting laser device comprises an array of laser regions and at least one detector region positioned between at least two laser regions. In such embodiments, two or more laser regions can share an integrated detector region. Alternatively, the surface-emitting laser device may comprise two or more laser regions and two or more corresponding integrated detector regions.

[0057] According to a second aspect of the present invention, a method for manufacturing a surface-emitting laser device is provided, and this method is, • A step of providing an active layer, The steps include providing a semiconductor layer optically bonded to an active layer, The steps include providing a first photonic crystal structure including an array of scattering centers arranged within a semiconductor layer, The step of providing a first laser region, wherein the first laser region is defined by a set of first electrical contacts arranged on opposite sides of a coupled active layer and a semiconductor layer, and is configured to generate a first output field of a surface-emitting laser device. The steps include providing a first detector region defined by a set of second electrical contacts located on opposite sides of the coupled active layer and semiconductor layer, outside the first laser region, The method comprises the step of configuring a first detector region to generate a first output current proportional to a first output field.

[0058] Embodiments of a second aspect of the present invention may include features for carrying out preferred or optional features of a first aspect of the present invention, and vice versa.

[0059] According to a third aspect of the present invention, a method for operating a surface-emitting laser device according to the first aspect is provided, and this method is The steps include: applying a voltage between a set of first electrical contacts to supply a drive current to a first laser region and generate an output field; The method comprises the step of generating an output current proportional to the output field within a first detector region.

[0060] Most preferably, the method of operating the surface-emitting laser device further includes the step of applying a reverse bias voltage to a first detector region via a second set of electrical contacts.

[0061] Preferably, the method of operating the surface-emitting laser device further includes the step of adjusting the drive current of the first laser region in response to the measured (or determined) output power of the output field.

[0062] Preferably, the method of operating the surface-emitting laser device further includes the step of adjusting the drive current of the first laser region so as to maintain the output field at a constant power.

[0063] Optionally, the method of operating the surface-emitting laser device further includes the step of supplying drive current to two laser regions to generate two output fields of the surface-emitting laser device.

[0064] Preferably, the method of operating the surface-emitting laser device further includes the step of interrupting the drive current to the first laser region and supplying a drive current to the second laser region in response to determining a failure or loss of function in the first laser region.

[0065] Preferably, the method of operating the surface-emitting laser device further includes the step of supplying a drive current to two or more laser regions and generating an output current from a first detector region that represents the total output power of the two or more laser regions.

[0066] Embodiments of a third aspect of the present invention may include features for carrying out preferred or optional features of the first and second aspects of the present invention, and vice versa. [Brief explanation of the drawing]

[0067] Hereinafter, various embodiments of the present invention will be described as examples with reference to the drawings. [Figure 1] Figure 1 shows (a) an exploded perspective view and (b) a cross-sectional view of a photonic crystal surface-emitting laser known as prior art. [Figure 2] Figure 2 shows a cross-sectional view of a photonic crystal surface-emitting laser device according to one embodiment of the present invention. [Figure 3] Figure 3 shows a cross-sectional view of a photonic crystal surface-emitting laser device according to an alternative embodiment of the present invention. [Figure 4] Figure 4 shows a cross-sectional view of a photonic crystal surface-emitting laser device according to an alternative embodiment of the present invention. [Figure 5] Figure 5 shows a cross-sectional view of a photonic crystal surface-emitting laser device according to an alternative embodiment of the present invention. [Figure 6] Figure 6 shows a cross-sectional view of a photonic crystal surface-emitting laser device according to an alternative embodiment of the present invention. [Figure 7] Figure 7 shows a photonic crystal surface-emitting laser device according to yet another alternative embodiment of the present invention. [Figure 8] Figure 8 shows a photonic crystal surface-emitting laser device according to yet another alternative embodiment of the present invention.

[0068] In the following description, the same reference numerals are used for similar parts throughout the specification and drawings. The drawings are not necessarily to scale, and the proportions of certain parts are exaggerated to better illustrate the details and features of the embodiments of the invention. [Modes for carrying out the invention]

[0069] A photonic crystal surface-emitting laser (PCSEL) device 14 according to one embodiment of the present invention and a method for manufacturing the same will be described with reference to Figure 2. Figure 2 shows a cross-sectional view of the PCSEL device 14 according to one embodiment of the present invention.

[0070] The PCSEL device 14 in Figure 2 has a similar semiconductor layer structure to the PCSEL 1 shown in Figures 1(a) and 1(b). However, within the PCSEL device 14, the photonic crystal structure 15 is located only within a specific region of the semiconductor layer 16. Therefore, unlike the photonic crystal layer 5 of the PCSEL 1 shown in Figures 1(a) and 1(b), the scattering centers of the photonic crystal structure 15 do not extend throughout the entire semiconductor layer 16. In other words, scattering centers are absent in at least a portion of the semiconductor layer 16.

[0071] The PCSEL device 14 in Figure 2 comprises a first set of electrical contacts 8a, 8b and a second set of electrical contacts 17a, 17b. The first set of electrical contacts 8a, 8b are arranged on opposite outer surfaces of the PCSEL device 14, more specifically, surrounding the region containing the photonic crystal structure 15. The positions of the first set of electrical contacts 8a, 8b define the laser region 18 of the PCSEL device 14. The upper electrical contact 8a has an aperture 11 through which the output field 10 of the PCSEL device 14 is extracted when the PCSEL device 14 is oscillating.

[0072] The second set of electrical contacts 17a and 17b are similarly provided on the outer surfaces of both sides of the PCSEL device 14 in an adjacent area, separate from the laser region 18. This defines the detector region 19 of the PCSEL device 14.

[0073] The structure of the PCSEL device 14 and the arrangement of the second pair of electrical contacts 17a and 17b allow the detector region 19 adjacent to the laser region 18 to function as an integrated photodetector.

[0074] A photodetector is a semiconductor device that converts light into electric current and is composed of p-type and n-type semiconductor materials. When light enters the pn junction of a photodetector, electron-hole pairs are generated, which are collected as a photocurrent. This current is proportional to the intensity of the incident light. A photodetector typically has two terminals, a positive and a negative electrode, which are used to generate an electric field within the diode, thereby converting the incident light into an electric current.

[0075] As those skilled in the art will understand, the structure of the PCSEL device 14 requires n-doped and p-doped semiconductor layers, thereby forming the pn junction required for the photodetector. Furthermore, the second set of electrical contacts 17a, 17b of the PCSEL device 14 provides electrical connections to the terminals required for the photodetector, so the structure of the PCSEL device 14 is suitable for operation as a photodetector with an integrated detector region 19. Preferably, the detector region 19 should be operated in reverse bias; that is, the negative terminal is connected to the p-type semiconductor layer and the positive terminal is connected to the n-type semiconductor material, although it can also function in zero bias.

[0076] When the PCSEL device 14 is in its normal operating state, light automatically enters (or is received by) the detector region 19. More specifically, when a voltage is applied to the laser region 18 of the PCSEL device 14 via the first set of electrical contacts 8a and 8b, the active layer 4 emits light. As mentioned above, the photonic crystal structure 15 within the PCSEL device 14 scatters light linearly in the in-plane direction as well as in the orthogonal out-of-plane direction. Therefore, some of the light propagating in-plane enters the detector region 19 of the semiconductor layer 16, but in this embodiment, the photonic crystal structure 15 is not present there.

[0077] When the in-plane optical field 20 from the photonic crystal structure 15 reaches the detector region 19, a current is generated as described above, providing a means for measuring and monitoring the output power of the output field 10. Furthermore, by using a suitable power control loop 13, fluctuations in the output power of the output field 10 can be compensated for, and a constant output power level can be maintained. The output power is proportional to the in-plane optical field, and the current generated is proportional to (or at least related to) the output power.

[0078] The PCSEL device 14 described above offers numerous advantages over prior art. By using an integrated detector region 19 instead of an external photodetector 12, the need for additional external optical elements is eliminated. This reduces undesirable power loss in such optical elements, making it possible to obtain maximum power in the output field 10 of the PCSEL device 14.

[0079] Furthermore, since the detector region 19 is integrated within the PCSEL device 14, it is no longer necessary to continuously align the in-plane optical field 20 with respect to the detector region 19. As a result, the user does not need to continuously align or calibrate the photodetector, simplifying the device and operating conditions for the user.

[0080] Furthermore, the overall footprint of the PCSEL device 14 is significantly reduced, which can be very important for some applications.

[0081] The PCSEL device 14 in Figure 2 may further comprise one or more wavelength-selective reflectors 21 located outside the semiconductor structure of the PCSEL device 14. The wavelength-selective reflectors 21 are designed to reflect light of a selected wavelength, i.e., the wavelength of the output field 10.

[0082] The positions of one or more wavelength-selective reflectors 21 are chosen to return the in-plane optical field 20 from the semiconductor layer 16 into the photonic crystal structure 15. Advantageously, this means that light leaving the laser region 18 and entering the detector region 19 does not significantly reduce the overall output power of the PCSEL device 14. This is because most of the light incident on the detector region 19 is reflected back to the laser region 18, where the output field 10 of the PCSEL device 14 is generated.

[0083] As those skilled in the art will understand, the photonic crystal structure 15 may be positioned at any suitable location within the semiconductor layer 16, and in fact, it may extend throughout the entire semiconductor layer 16. Furthermore, the semiconductor layer 16 itself may be positioned at a different location within the stacked structure of the PCSEL device 14. Also, as described in relation to Figure 1, one or more additional layers may be provided within the PCSEL device 14 as needed.

[0084] For example, the PCSEL device 14 may further include a first isolated-confinement heterostructure (SCH) layer located between the lower cladding layer 3 and the active layer 4, and a second isolated-confinement heterostructure (SCH) layer located between the upper cladding layer 6 and the active layer 4.

[0085] Figure 3 shows a PCSEL device 22 according to an alternative embodiment of the present invention. This PCSEL device 22 has a structure similar to that shown in Figure 2, but in Figure 3, both the first photonic crystal structure 15a and the second photonic crystal structure 15b are provided within the semiconductor layer 16 of the PCSEL device 22.

[0086] Furthermore, a third set of electrical contacts 23a and 23b are provided on the outer surface of the PCSEL device 22 within the region containing the second photonic crystal structure 15b. Both sets of electrical contacts 8a and 23a have apertures 11a and 11b from which the output fields 10a and 10b of the PCSEL device 22 can be extracted. Thus, the PCSEL device 22 provides two separate laser regions 18a and 18b, and consequently two output fields 10a and 10b. The electrical contacts 8 and 23 define the first laser region 18a and the second laser region 18b of the PCSEL device 22.

[0087] When a voltage is applied to the PCSEL device 22 via the first set of electrical contacts 8a and 8b, a first in-plane optical field 20a from the first photonic crystal structure 15a propagates to the adjacent detector region 19. Similarly, when a voltage is applied to the PCSEL device 22 via the third set of electrical contacts 23a and 23b, a second in-plane optical field 20b from the second photonic crystal structure 15b propagates to the detector region 19.

[0088] The advantage of the above structure is that the overall lifespan of the PCSEL device 22 is significantly extended compared to the PCSEL device 14 shown in Figure 2 above. The lifespan of a PCSEL depends on various factors, including operating conditions and manufacturing quality. Typically, at the end of the PCSEL's lifespan, the user needs to replace the system, which can lead to undesirable downtime and may be undesirable in certain applications.

[0089] As described above, the lifespan of the PCSEL device 22 can be significantly extended by using the structure of the PCSEL device 22. In this case, voltage is initially applied to the PCSEL device 22 via electrical contacts 8a and 8b, but not to electrical contacts 23a and 23b. Therefore, the output field 10a is generated by the PCSEL device 22, and the power of the first in-plane optical field 20a is monitored by the integrated detector region 19, thereby maintaining the first output field 10a at a constant power level.

[0090] When the integrated detector area 19 detects that the output field 10a has dropped below a certain power level, or other signs of laser failure, the appropriate power control system 24 is used to switch to the second output 10b. Specifically, the voltage across electrical contacts 8a and 8b is interrupted, and instead, voltage is applied to the PCSEL device 22 via electrical contacts 23a and 23b. Thus, the output field 10b is generated by the PCSEL device 22, and the power of the second in-plane optical field 20b is monitored by the integrated detector area 19. Since the second output field is monitored by the same integrated detector area 19, it is ensured that the output field 10b is generated with the same constant output power as the first output field 10a. In this way, the user can continue to use the laser without interruption. The output from the PCSEL device 22 is maintained at a constant power level, significantly extending the overall lifespan of the device.

[0091] Please note that since the first output field 10a and the second output field 10b are spatially separated, the user may need to re-adjust the position of the output beam when switching between each output field. For example, an additional alignment optical system may be required to guide the second output field 10b to the same beam path as the first output field 10a.

[0092] Note that in another operating mode, both sets of electrical contacts may simultaneously supply drive current to both laser regions 18a and 18b, thereby simultaneously generating both output fields 10a and 10b. In this operating mode, the detector region 19 generates a current that represents the combined output power of the first laser region 18a and the second laser region 18b. This approach can also be scaled up so that the integrated detector region 19 measures the output power of a PCSEL device having an array of laser regions 18.

[0093] Figure 4 shows a PCSEL device 25 according to an alternative embodiment of the present invention.

[0094] In Figure 4, a first photonic crystal structure 15a, a second photonic crystal structure 15b, and a third photonic crystal structure 15c are provided within the semiconductor layer 16 of the device. Additional sets of electrical contacts 26a and 26b are provided, defining a third laser region 18c. This allows the PCSEL device 25 to generate an additional third output field 10c from the third laser region 18c, which includes the third photonic crystal structure 15c.

[0095] The PCSEL device 25 also includes a first detector region 19a and a second detector region 19b within its structure. The first detector region 19a and the second detector region 19b are provided with sets of electrical contacts 17a, 17b and 27a, 27b, respectively, on the outer surface of the device. As a result, the in-plane optical fields 20a, 20b from the first photonic crystal structure 15a and the second photonic crystal structure 15b are incident on (or received by) the first detector region 19a, and the in-plane optical field 20c generated by the third photonic crystal structure 15c is incident on (or received by) the second detector region 19b. It is also possible to confine the in-plane optical fields to their respective adjacent detector regions (i.e., effectively separate the detector regions 19a, 19b from each other) by placing optional reflective elements (not shown) between adjacent laser regions 18a, 18b, 18c.

[0096] The structure of the PCSEL device 25 can be used to provide a device with multiple output fields 10a, 10b, and 10c, and constant power monitoring in the integrated detector regions 19a, 19b ensures that the combined output power of the output fields 10a, 10b, and 10c remains constant. Furthermore, as illustrated in Figure 3, the lifespan of the PCSEL device 25 can be extended by operating the PCSEL device 25 to generate only one output field 10a, 10b, or 10c at a time. It is also conceivable that this device could generate two output fields from two laser regions while providing redundancy with a third laser region in case one of the two laser regions fails or degrades.

[0097] As those skilled in the art will understand, it is possible to add any number of additional laser regions 18 (with corresponding electrical contacts) within the PCSEL device 25 to generate any number of additional output fields 10. Similarly, it is possible to increase the number of integrated detector regions 19 so that the power of each output field 10 generated by the additional laser regions 18 is monitored. As described above, it is also possible for a single detector region 19 to monitor the output of multiple laser regions 18 or an array of laser regions 18.

[0098] Figure 5 shows a PCSEL device 28 according to an alternative embodiment of the present invention.

[0099] Similar to Figure 3, a single integrated detector region 19 is provided within the PCSEL device 28, along with a first photonic crystal structure 15a and a second photonic crystal structure 15b located within the semiconductor layer 16. A first set of electrical contacts 8 and a third set of electrical contacts 23 define corresponding laser regions 18a and 18b on either side of the detector region 19, respectively. However, in Figure 5, the first output field 10a and the second output field 10b are emitted from the PCSEL device 28 at a significantly different angle than in the previously described embodiments, for example, to be coupled to a single output coupler 29.

[0100] There are various approaches to changing the direction of the output field 10 from the PCSEL device 28. One approach is to use a beam steering optical system outside the PCSEL device 28. For example, a micro-electromechanical system (MEMS) mirror can be placed in the beam path of the PCSEL device 28 to deflect the output beam in the desired direction. However, this approach requires additional optical elements, thus increasing the device's footprint.

[0101] Another approach to changing the direction of the output field 10 is to modify the shape of the photonic crystal structure 15. This involves changing the size, shape, or orientation of the scattering centers of the photonic crystal structure 15 to promote radiation in a specific direction. However, this approach may make it difficult to control or change the direction of the output beam as needed.

[0102] A further alternative method, shown in Figure 5, involves modulating the first photonic crystal structure 15a and the second photonic crystal structure 15b with a modulation pattern to change the direction of the output fields 10a and 10b. By applying a voltage to the first photonic crystal structure 15a and the second photonic crystal structure 15b, a modulation pattern can be formed in the refractive index, which can then be used to control the direction of the output fields 10a and 10b. This modulation pattern allows the PCSEL device 28 to radiate in two or more directions simultaneously, as shown in Figure 5. Additional output fields 30a and 30b are shown by dashed lines in Figure 5, and their presence limits the power achievable in output fields 10a and 10b, respectively.

[0103] This approach provides an integrated and flexible method for controlling the direction of the output fields 10a and 10b of the PCSEL device 28. For example, by modulating the voltage pattern, the output fields 10a and 10b can be directed in any desired output direction.

[0104] As shown in Figure 5, the output directions of output fields 10a and 10b are selected so that both are guided into the output coupler 29. In particular, the output angles of the first output field 10a and the second output field 10b are selected to achieve maximum coupling to the output coupler 29, which is located at the center between the output fields 10a and 10b.

[0105] The lifespan of the PCSEL device 28 can be extended by initially generating only the first output field 10a (as in the PCSEL device 22 in Figure 3), and then switching to the second output field 10b using an appropriate power control system 24 when the power of the first output field 10a decreases due to aging of the semiconductor structure or other reasons.

[0106] Since the in-plane optical fields 20a and 20b generated by the photonic crystal structures 15a and 15b can both be monitored by the integrated detector region 19, a constant output power of the PCSEL device 28 can be continuously maintained, for example, using the power control system 24 described above.

[0107] Since both the first output field 10a and the second output field 10b are aligned to the same output coupler 29, there is no need to readjust the position of the PCSEL device 28 when switching between the output fields 10a and 10b. Therefore, the device requires less user input compared to previous embodiments, and its lifespan is extended. As a result, the PCSEL device 28 is easy to use and advantageous in applications where high output is not critical.

[0108] Figure 6 shows a PCSEL device 31 according to an alternative embodiment of the present invention. The PCSEL device 31 is similar to the one shown in Figure 5, but the output coupler 29 is positioned directly above the first laser region 18a, which includes the first photonic crystal structure 15a. Therefore, modulation of the first photonic crystal structure 15a is not required to couple the first output field 10a to the output coupler 29. However, the second photonic crystal structure 15b is modulated to generate the output field 10b at an angle that provides maximum coupling efficiency into the output coupler 29. Note that the maximum output power of the output field 10b is limited because an additional output field 30b is generated.

[0109] Similar to the embodiments described above, the integrated detector region 19 can monitor the in-plane optical fields 20a and 20b, thereby maintaining a constant output power for the PCSEL device 31.

[0110] As those skilled in the art will understand, alternatively, the output coupler 29 can be positioned at any suitable location to enable the coupling of the first output field 10a and the second output field 10b through modulation of the first photonic crystal 15a and / or the second photonic crystal 15b. It is also conceivable that MEMS approaches and / or geometric approaches to beam steering may be used in addition to, or instead of, the modulation approaches in any variation of the relevant embodiment.

[0111] Figure 7 shows a PCSEL device 32 according to an alternative embodiment of the present invention. The PCSEL device 32 comprises four laser regions 18a to 18d defined by electrical contacts 8, 23, 26, and 27, which generate output fields 10a to 10d.

[0112] The in-plane optical field from each photonic crystal is monitored by an integrated detector region 19 located between all four laser regions 18a–18d. The photonic crystal structures 15a–15d are arranged and modulated so that each of the four output fields 10a–10d is coupled to the output coupler 29, although any beam steering approach is also conceivable.

[0113] As a result, the PCSEL device 32 can have a significantly longer lifespan compared to the embodiments described in Figures 5 and 6 (potentially more than four times the lifespan of a PCSEL containing a single laser region). Furthermore, by appropriately modulating the photonic crystal structures 15a to 15d, there is no need to readjust the position when switching between the output fields 10a to 10d. The integrated detector region 19 allows monitoring of the in-plane optical field from each photonic crystal structure, enabling the PCSEL device 32 to maintain each output field 10a to 10d at a constant power.

[0114] Figure 8 shows a PCSEL device 33 according to a further alternative embodiment of the present invention.

[0115] The PCSEL device 33 similarly comprises laser regions 18a to 18d and generates four output fields 10a to 10d. However, in this case, the output coupler 29 is positioned directly above the laser region 18a where the first photonic crystal structure 15a exists. Therefore, there is no need to modulate the first photonic crystal 15a. The other photonic crystals 15b to 15d are appropriately modulated to direct the output fields 10c to 10d to the output coupler 29.

[0116] As those skilled in the art will understand, the output coupler 29 can be positioned at any suitable location that enables coupling of each of the four output fields 10a to 10d through modulation of the photonic crystal structures 15a to 15d. Furthermore, the integrated detector region 19 can be positioned at any suitable alternative location, as long as it allows in-plane optical fields from the photonic crystal structures 15a to 15d to be incident on the integrated detector region 19.

[0117] Furthermore, as will be understood by those skilled in the art, it is also possible to add an additional laser region 18 to the PCSEL device 33 to generate a larger output field 10, thereby further extending the lifespan of the PCSEL device 33. If necessary, an integrated additional detector region 19 can also be provided within the PCSEL device 33 to monitor the in-plane optical field generated by the photonic crystal structure 15.

[0118] In summary, the present invention provides an alternative surface-emitting laser device that differs from those known in the prior art, with improved structure and operating parameters. In particular, the present invention provides a photonic crystal surface-emitting laser (PCSEL) device that provides a detector area integrated within the structure of the PCSEL device. The disclosed PCSEL device enables improved power monitoring for easier stabilization of output power. Furthermore, the structure of the disclosed PCSEL device results in a smaller footprint and reduces the need for continuous input and alignment by the device user.

[0119] This specification discloses a surface-emitting laser device and a method for manufacturing and operating the same. The surface-emitting laser device comprises an active layer, a semiconductor layer optically coupled to the active layer, and a photonic crystal structure disposed within the semiconductor layer. The device further comprises a laser region and a detector region. The laser region includes a first set of electrical contacts located on opposite sides of the active layer and the semiconductor layer, generating the device's output field. The detector region includes a second set of electrical contacts located on opposite sides of the active layer and the semiconductor layer, and situated outside the first laser region. The detector region is configured to generate an output current proportional to the output field. The presence of the detector region within the device improves the structure and enhances power monitoring techniques compared to the prior art.

[0120] Throughout this specification, unless otherwise specified in the context, the terms “comprise” or “include,” or variations such as “comprises” or “comprising,” “includes” or “including,” should be understood to mean that they include the elements or groups of elements described, but not that they exclude other elements or groups of elements.

[0121] Furthermore, references to prior art in this specification should not be interpreted as indicating that the prior art constitutes part of common technical knowledge.

[0122] The above description of the present invention is presented for illustrative and explanatory purposes and is not intended to be exhaustive or to limit the invention to the exact form of the disclosure. The embodiments described have been selected and described to best illustrate the principles of the invention and their practical applications, thereby enabling those skilled in the art to best utilize the invention in various embodiments and variations suited to specific intended applications. Accordingly, further changes or improvements can be incorporated without departing from the scope of the invention as defined by the appended claims.

Claims

1. A surface-emitting laser device, The active layer, A semiconductor layer optically bonded to the active layer, A first photonic crystal structure including an array of scattering centers arranged within the semiconductor layer, A first laser region defined by a set of first electrical contacts arranged on opposite sides of the bonded active layer and semiconductor layer, configured to generate a first output field of the surface-emitting laser device, Outside the first laser region, a first detector region is defined by a set of second electrical contacts arranged on opposite sides of the coupled active layer and semiconductor layer, and configured to generate a first output current proportional to the first output field. A surface-emitting laser device characterized by comprising the following features.

2. In the surface-emitting laser device according to claim 1, A surface-emitting laser device characterized in that the first photonic crystal structure is configured to provide an in-plane optical field within the semiconductor layer.

3. In the surface-emitting laser device according to claim 2, A surface-emitting laser device characterized in that the first detector region is configured to detect an in-plane optical field generated by the photonic crystal structure.

4. In the surface-emitting laser device according to claim 2 or 3, A surface-emitting laser device characterized in that the first detector region provides feedback to a control loop, and the control loop adjusts the output power of the first output field by compensating for changes in the detected power of the in-plane optical field.

5. In the surface-emitting laser device according to any one of claims 1 to 4, A surface-emitting laser device characterized in that the first detector region is operated with a reverse bias.

6. In the surface-emitting laser device according to any one of claims 1 to 5, A surface-emitting laser device further comprises two or more laser regions, each characterized by a set of electrical contacts, wherein each of the two or more laser regions is configured to generate a separate output field of the surface-emitting laser device.

7. In the surface-emitting laser device according to claim 6, A surface-emitting laser device characterized in that the first detector region is configured to detect an in-plane optical field generated in each of the two or more laser regions.

8. In the surface-emitting laser device according to claim 6 or 7, A surface-emitting laser device characterized in that the first detector region provides feedback to a control loop, and the control loop is configured to selectively operate one of the two or more laser regions to generate a single output field.

9. In the surface-emitting laser device according to claim 8, A surface-emitting laser device characterized in that the control loop is configured to automatically switch to selectively operating one of the remaining laser regions when the currently selected laser region ceases to generate the required output power.

10. In the surface-emitting laser device according to any one of claims 6 to 9, A surface-emitting laser device characterized in that the surface-emitting laser further comprises an output coupler.

11. In the surface-emitting laser device according to claim 10, A surface-emitting laser device characterized in that the two or more laser regions are configured to guide the associated output fields to the output coupler.

12. In the surface-emitting laser device according to claim 11, A surface-emitting laser device characterized in that the direction of the output field from one or more laser regions is controlled by modulating the photonic crystal structure with a modulation pattern.

13. In the surface-emitting laser device according to claim 11 or 12, A surface-emitting laser device characterized in that the direction of the output field from one or more laser regions is controlled by changing the size, shape, and / or orientation of the scattering centers of the photonic crystal structure.

14. In the surface-emitting laser device according to any one of claims 11 to 13, The surface-emitting laser device further comprises a beam steering optical system configured to adjust the direction of the output field from one or more laser regions.

15. In the surface-emitting laser device according to any one of claims 6 to 14, The surface-emitting laser device further comprises two or more integrated detector regions, each of which is characterized by a set of electrical contacts, and each of the two or more integrated detector regions is configured to generate an output current proportional to the one or more output fields.

16. In the surface-emitting laser device according to claim 15, A surface-emitting laser device characterized in that each of the two or more integrated detector regions is configured to detect an in-plane optical field generated within the two or more laser regions.

17. In the surface-emitting laser device according to any one of claims 1 to 16, A surface-emitting laser device characterized in that a wavelength-selective reflector is arranged outside the semiconductor layer containing the photonic crystal structure.

18. A method for manufacturing a surface-emitting laser device, - A step of providing an active layer, - The step of providing a semiconductor layer optically bonded to the active layer, - Providing a first photonic crystal structure including an array of scattering centers arranged within the semiconductor layer, - A step of providing a first laser region, wherein the first laser region is defined by a set of first electrical contacts arranged on opposite sides of a coupled active layer and a semiconductor layer, and is configured to generate a first output field of the surface-emitting laser device. - Providing a first detector region defined by a set of second electrical contacts located outside the first laser region, with the coupled active layer and semiconductor layer on opposite sides of each other; - The step of configuring the first detector region to generate a first output current proportional to the first output field. A method characterized by comprising:

19. In a method for operating a surface-emitting laser device according to any one of claims 1 to 17, - A step of applying a voltage between the set of first electrical contacts to supply a drive current to the first laser region and generate an output field, - A step of generating an output current proportional to the output field within the first detector region. A method characterized by comprising:

20. In the method of operating a surface-emitting laser device according to claim 19, A method further comprising the step of applying a reverse bias voltage to the first detector region via the second set of electrical contacts.

21. In the method of operating a surface-emitting laser device according to claim 19 or 20, A method further comprising the step of adjusting the drive current of the first laser region in response to the measured output power of the output field.

22. In the method of operating the surface-emitting laser device according to claim 21, A method further comprising the step of adjusting the drive current of the first laser region so as to maintain the output field at a constant power.

23. In a method for operating a surface-emitting laser device according to any one of claims 19 to 22, A method further comprising the step of supplying a drive current to a first laser region and a second laser region to generate two output fields of the surface-emitting laser device.

24. In the method of operating the surface-emitting laser device according to claim 23, A method further comprising the step of interrupting the drive current to the first laser region and supplying a drive current to the second laser region in response to determining a failure or loss of function in the first laser region.

25. In a method for operating a surface-emitting laser device according to any one of claims 19 to 24, A method further comprising the steps of supplying a drive current to two or more laser regions and generating an output current from the first detector region that represents the total output power of the two or more laser regions.

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