Directly modulated laser

Abstract

A laser includes a substrate, a first cladding and a second cladding, a gain medium, and a plurality of supports. The first cladding is spaced apart from the substrate by an air gap. The first cladding has a thickness in a vertical direction in a range from 0.05 microns to 0.15 microns. The gain medium is disposed on the first cladding opposite the air gap. The second cladding is disposed on the gain medium opposite the first cladding. The second cladding has a thickness in the vertical direction in a range from 0.05 microns to 0.15 microns. The supports are coupled to each of the substrate, the first cladding, the gain medium, and the second cladding to hold the first cladding, the gain medium, and the second cladding spaced apart from the substrate.

Description

Technical Field

[0001] The embodiments discussed in this invention relate to direct modulated lasers (DMLs). Background Technology

[0002] Unless otherwise stated in this disclosure, the materials described herein are not prior art to the claims of this application and should not be considered prior art by virtue of their inclusion in this section.

[0003] The speed of a directly modulated laser is partly limited by the ratio between the optical confinement factor and the volume of the active region of the laser. This ratio defines the intensity of the interaction between gain and light. In lasers with normal ridge or buried heterostructures, this ratio is limited by the exponential contrast between the semiconductor core multiple quantum well (MQW) material and the surrounding cladding.

[0004] The subject matter claimed in this disclosure is not limited to implementations that address any shortcomings or operate only in environments such as those described above. Rather, this background is provided merely to illustrate an example technical field in which some of the implementations described in this disclosure can be practiced. Summary of the Invention

[0005] This summary is provided to introduce a series of concepts in a simplified form, which will be further described in the detailed embodiments below. This summary is not intended to identify key features or essential characteristics of the claimed subject matter, nor is it intended to help determine the scope of the claimed subject matter.

[0006] In the example, the laser includes a substrate, a first cladding member and a second cladding member, a gain medium, and a plurality of supports. The first cladding member is spaced from the substrate by an air gap. The thickness of the first cladding member in the vertical direction ranges from 0.05 micrometers to 0.15 micrometers. The gain medium is disposed on the first cladding member opposite to the air gap. The second cladding member is disposed on the gain medium opposite to the first cladding member. The thickness of the second cladding member in the vertical direction ranges from 0.05 micrometers to 0.15 micrometers. Supports are connected to each of the substrate, the first cladding member, the gain medium, and the second cladding member to hold the first cladding member, the gain medium, and the second cladding member spaced apart from the substrate.

[0007] In another example, the laser includes a substrate, a waveguide, and a low-reflection (LR) mirror. The waveguide is spaced from the substrate by an air gap. The waveguide includes a distributed feedback (DFB) active section, a passive section, and a distributed Bragg reflector (DBR) section. The passive section is inline with the DFB active section. The DBR section is inline with the DFB active section. The DBR active section is located between the passive section and the DBR section. The low-reflection mirror is formed at the front of the passive section of the waveguide.

[0008] In another example, a method of forming a laser includes depositing a sacrificial layer on a substrate. The method includes forming a waveguide on the sacrificial layer, the waveguide including a first cladding and a second cladding, and a gain dielectric located between the first cladding and the second cladding. The method includes forming a first current-blocking structure laterally adjacent to a first side of the waveguide. The method includes forming a second current-blocking structure laterally adjacent to a second side of the waveguide, the second side of the waveguide being opposite to the first side of the waveguide. The method includes forming an air gap between the substrate and the waveguide by selectively etching the sacrificial layer through a hole extending through one of the first and second current-blocking structures to the sacrificial layer.

[0009] Additional features and advantages of the invention will be set forth in the description which follows, and will become apparent in part from that description, or may be learned by practice of the invention. The features and advantages of the invention can be realized and obtained by means of the instruments and combinations specifically pointed out in the appended claims. These and other features of the invention will become more fully apparent from the following description and the appended claims, or may be learned by practice of the invention as set forth below. Attached Figure Description

[0010] To further illustrate the above and other advantages and features of the present invention, the invention will be described in more detail with reference to specific embodiments illustrated in the accompanying drawings. It should be understood that these drawings depict only typical embodiments of the invention and should therefore not be considered as limiting the scope of the invention. The invention will be described and explained with additional features and details using the accompanying drawings, in which:

[0011] Figure 1 This is a cross-sectional view of an example laser with strong light confinement caused by air.

[0012] Figure 2 Here is a block diagram of another example laser;

[0013] Figure 3 This is a top frontal stereoscopic view of another example laser with strong light limitation caused by air.

[0014] Figures 4A to 4J The illustration shows a set of example epitaxial processing steps for forming a laser with strong light confinement caused by air;

[0015] Figure 5 This is a flowchart of an example method for forming a laser;

[0016] Figure 6 The diagram illustrates the simulated S21 response of the example laser as a function of the modulation frequency;

[0017] Figure 7 The illustration shows a simulated optical mode in the vertical direction of an example laser with strong light confinement caused by air; and

[0018] Figure 8 The illustration shows the simulated optical confinement as a function of the air gap thickness for an example laser with strong optical confinement caused by air.

[0019] All are arranged in accordance with at least one of the embodiments described herein. Detailed Implementation

[0020] In 2019, Yamaoka et al. described an air / semiconductor combination to provide strong exponential contrast for the strong optical confinement of directly modulated lasers. See their paper, accepted after the deadline at ECOC 2019: 239.3-Gbit / s NET RATE PAM-4 TRANSMISSION USING DIRECTLY MODULATED MEMBRANE LASERS ON HIGH-THERMAL-CONDUCTIVITY SiC. According to Yamaoka et al., in state-of-the-art directly modulated lasers, the inherent 3 dB bandwidth f... 3dB Subject to relaxation oscillation frequency f r Due to limitations of parameters such as f, the relaxation oscillation frequency is... r Furthermore, direct-modulation lasers may be limited by poor heat dissipation. Therefore, Yamaoka et al. described a direct-modulation laser wafer attached to a silicon carbide (SiC) substrate to improve heat dissipation. Yamaoka et al.'s direct-modulation laser wafer is attached to the SiC substrate via a thin layer, for example, 40 nanometers (nm) thick, formed of silicon dioxide (SiO2). This configuration induces strong strain, which can adversely affect the reliability of such direct-modulation lasers.

[0021] Some embodiments described herein relate to a laser structure for a directly modulated laser that provides strong optical confinement and good heat dissipation through air, while avoiding the strong strain that can adversely affect reliability in the configuration of Yamaoka et al. The laser structure for a directly modulated laser as described herein may include a waveguide spaced from a substrate by an air gap. The waveguide may include a gain medium, such as a multi-quantum well core encased by a thin first / lower cladding and a second / upper cladding. Each of the first and second claddings may, for example, have a thickness of about 0.1 micrometers, or more generally, a thickness in the range of 0.05 to 0.15 micrometers. The waveguide may be suspended spaced from or supported above the substrate by pillars or supports formed of a material with high thermal conductivity. As used herein, high thermal conductivity may include 0.50 W / cm². -1 ℃ -1 Or higher thermal conductivity. The support can be indium phosphide (InP) or may include indium phosphide, which can have a thermal conductivity of approximately 0.68 W / cm². -1 ℃ -1 The thermal conductivity. Therefore, the relaxation oscillation frequency f r It is not limited by the thermal dissipation characteristics of the laser structure of directly modulated lasers.

[0022] Some embodiments of the laser structure for the direct-modulated laser described herein can have a distributed reflector (DR) with a weak optical feedback (R) laser cavity design, also known as a DR+R laser. According to some embodiments, DR+R lasers are typically implemented in waveguides spaced from the substrate by an air gap to provide strong optical confinement. DR+R lasers can combine aspects of distributed reflector lasers and distributed feedback (DFB)+R lasers. Example aspects of distributed reflector lasers, DFB+R lasers, and DR+R lasers will be described sequentially.

[0023] Generally, a distributed reflector laser can include an active region with a distributed feedback grating, also known as a distributed feedback region, and a passive region with a distributed Bragg reflector (DBR) grating, also known as a distributed Bragg reflector region, optically coupled to the active region. The laser wavelength in the distributed feedback region is aligned with the long-wavelength edge of the reflection profile peak in the distributed Bragg reflector region. Intensity modulation in the distributed feedback region is accompanied by frequency chirp; for example, the frequency changes to shorter wavelengths as modulation progresses from a bias of 0 to a bias of 1, and to longer wavelengths as modulation progresses from a bias of 1 to a bias of 0. The frequency chirp caused by intensity modulation causes the reflection in the distributed Bragg reflector region to change as the frequency of the laser mode shifts up and down at the long-wavelength edge of the reflection profile peak in the distributed Bragg reflector region. When the distributed reflector laser is detuned such that the laser mode is located at the long-wavelength edge of the reflection profile peak, the frequency chirp caused by intensity modulation in the distributed feedback region translates into an effective enhancement of differential gain, increased modulation speed, and / or increased bandwidth. This can be referred to as the detuning load effect. Exemplary distributed reflector lasers and other details regarding detuned loading effects are described in U.S. Patent No. 10,461,503, which is incorporated herein by reference.

[0024] Generally, a DFB+R laser can include an active region and a passive region, the passive region comprising a passive waveguide optically coupled to the active region. The active region of the DFB+R laser includes a distributed feedback grating and can therefore be referred to as the distributed feedback region. The DFB+R laser also includes a low-reflection (LR) mirror located on the front side of the passive region. The reflectivity of the LR mirror can be approximately 3% or some other relatively low value. The resulting DFB+R laser has a complex cavity design including an etalon (formed between the portion of the distributed feedback grating at the front of the distributed feedback region and the LR mirror). The etalon is configured to dynamically modify the cavity loss due to frequency chirp when the distributed feedback section is modulated, for example, by aligning the laser mode of the distributed feedback region with the long-wavelength edge of the etalon's reflection profile peak, to leverage the detuning loading effect and improve the differential gain, speed, and / or bandwidth of the DFB+R laser. An exemplary DFB+R laser is described in U.S. Patent Application No. 16 / 691,549, filed November 21, 2019, which is incorporated herein by reference.

[0025] In general, DR+R lasers can combine aspects of distributed reflector lasers and DFB+R lasers. For example, a DR+R laser may include a distributed feedback region, a distributed Bragg reflector region, a passive waveguide, and a low-reflection mirror. In some embodiments, the distributed Bragg reflector region is optically coupled to the rear of the distributed feedback region, and the passive waveguide is optically coupled to the front of the distributed feedback region between the distributed feedback region and the low-reflection mirror. Similar to DFB+R lasers, in DR+R lasers, an etalon may be formed between the low-reflection mirror and the front portion of the distributed feedback grating in the distributed feedback region. DR+R lasers can utilize the detuning loading effect by aligning the laser mode of the distributed feedback region with the long-wavelength edge of the reflection profile peak of the distributed Bragg reflector region and / or the etalon.

[0026] The implementations described herein can alternatively or additionally utilize the photon-photon resonance (PPR) effect to improve performance. When a directly modulated laser, such as a distributed feedback laser or a distributed Bragg reflector laser, is modulated, the modulation sidebands broaden the directly modulated laser spectrum around the master laser mode. If a sidemode of the laser cavity is present in the modulation spectrum, this sideband can be coupled to the sidemode and resonantly amplified. This effect is called the photon-photon resonance effect, and it can enhance the modulation response around frequencies corresponding to the frequency difference between the master mode and the sidemode. The frequency interval between the laser mode and the photon-photon resonance mode can be called the photon-photon resonance frequency. Further details regarding the photon-photon resonance effect are described in U.S. Patent No. 10,461,503 and U.S. Patent Application No. 16 / 691,549.

[0027] In some implementations, the DR+R laser or other directly modulated lasers described herein may have a 3-dB bandwidth of 150 GHz or higher, such as 160 GHz or even higher. Alternatively or additionally, some implementations of the DR+R laser or other directly modulated lasers described herein are capable of transmitting optical signals at data rates of 200 gigabits per second (Gb / s) or higher.

[0028] Various aspects of exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. It should be understood that the drawings are illustrations and schematic representations of these exemplary embodiments and are not intended to limit the invention, nor are they necessarily drawn to scale.

[0029] Figure 1This is a cross-sectional view of an example laser 100 arranged according to at least one embodiment described herein, having strong light confinement caused by air. Generally, the laser 100 includes a substrate 102 and a waveguide 104 spaced apart from the substrate 102 by an air gap 106.

[0030] also, Figure 1 Including arbitrarily defined xyz axes, where the x-axis is in Figure 1 The center is roughly aligned laterally, and the y-axis is... Figure 1 The center is roughly vertically aligned, and the z-axis is in Figure 1 Align the laser beam along the direction of the page entrance or vertical alignment. As used herein, terms such as vertical, length, and their variations refer to the direction of laser light propagation, which is located in... Figure 1 The entry and exit points are parallel to the z-axis. Terms and variations such as lateral, height, thickness, top, bottom, and vertical refer to the direction perpendicular to the light propagation direction and perpendicular to the surface 102A of the substrate 102—where the waveguide 104 is formed to be spaced apart from the substrate 102; this direction is in Figure 1 The center is vertical and parallel to the y-axis. Terms and variations such as lateral, width, and side refer to a direction perpendicular to both the direction of light propagation and the transverse direction; this direction is... Figure 1 The middle is lateral and parallel to the x-axis.

[0031] As used herein, the term "light" should be interpreted broadly as any electromagnetic radiation that can be used for optical communication. Therefore, light can include electromagnetic radiation in the following bands: O band (~1261 nm to 1361 nm), E band (~1361 nm to 1461 nm), S band (~1461 nm to 1531 nm), C band (~1531 nm to 1561 nm), L band (~1561 nm to 1625 nm), 850 nm band, or other bands.

[0032] Return to Figure 1 Waveguide 104 includes a gain medium 108, such as a multiple quantum well, which is vertically positioned within waveguide 104 between a first cladding 110 (or lower cladding) and a second cladding 112 (or upper cladding). As shown, the gain medium 108 is arranged on the first cladding 110 opposite to the air gap 106, and the second cladding 112 is arranged on the gain medium 108 opposite to the first cladding 110. In some implementations, the thickness of the first cladding 110 is in the range of 0.05 micrometers to 0.15 micrometers or is approximately 0.1 micrometers, and the thickness of the second cladding 112 is in the range of 0.05 micrometers to 0.15 micrometers or is approximately 0.1 micrometers.

[0033] In addition, the laser 100 includes a plurality of support members 114, in Figure 1 Only two of the plurality of support members 114 are visible in the cross-sectional view. Each of the support members 114 can be connected to each of the substrate 102, the first cover member 110, the gain medium 108, and the second cover member 112 to hold or support the first cover member 110, the gain medium 108, and the second cover member 112 at a distance from the substrate 102.

[0034] In some embodiments, a first current blocking structure 116 and a second current blocking structure 118 are laterally positioned adjacent to opposite sides of the waveguide 104. More specifically, the first current blocking structure 116 is laterally positioned adjacent to the first side of the waveguide 104. Figure 1 The first side portion of waveguide 104 (the middle part being the left side) may include the first cladding 110, the gain dielectric 108, and the first side portion of the second cladding 112. The second current blocking structure 118 is laterally positioned adjacent to the second side portion of waveguide 104. Figure 1 (The middle part is the left side). The second side of waveguide 104 may include the second side of the first cladding 110, the gain medium 108, and the second cladding 112. In some embodiments, part or all of each of the first current blocking structure 116 and the second current blocking structure 118 may be configured with waveguide 104 to substantially or completely confine light within waveguide 104 and may therefore be considered part of waveguide 104.

[0035] The support member 114 may be integrally formed in the first current blocking structure 116 and the second current blocking structure 118. For example, as further described elsewhere herein, the first current blocking structure 116 and the second current blocking structure 118 may be partially formed on the substrate 102 and partially formed on the first cladding member 110 and coupled to each of the substrate 102, the first cladding member 110, the gain medium 108, and the second cladding member 112. The first current blocking structure 116 and the second current blocking structure 118 arranged in this way remain coupled to each of the substrate 102, the first cladding member 110, the gain medium 108, and the second cladding member 112 when the sacrificial layer between the first cladding member 110 and the substrate 102 is removed during the manufacturing process of the laser 100, to support the first cladding member 110, the gain medium 108, and the second cladding member 112 spaced apart from the substrate 102 by the air gap 106, and thus can be used as the support member 114.

[0036] Each of the first current blocking structure 116 and the second current blocking structure 118 may include indium phosphide or other suitable materials. In some examples, the first current blocking structure 116 includes p-doped indium phosphide and the second current blocking structure 118 includes n-doped indium phosphide. Alternatively or additionally, the substrate 102 may include indium phosphide.

[0037] An anode 120 can be formed on the first current blocking structure 116. A cathode 122 can be formed on the second current blocking structure 118. Current can be injected into the laser 100 through the anode 120, and the current can travel substantially laterally from the anode 120 through the waveguide 104, including through the gain medium 108, to the cathode 122.

[0038] Figure 2 This is a block diagram of another example laser 200 arranged according to at least one embodiment described herein. Although not included in... Figure 2 As shown, however, laser 200 can typically be formed in a waveguide spaced apart from the substrate to create strong optical confinement through air. For example, laser 200 can typically be formed in... Figure 1 In the waveguide 104 that is spaced apart from the substrate 102 by the air gap 106.

[0039] The laser 200 includes an active section 202, a passive section 204 aligned with the active section 202, and a low-reflection mirror 206 formed in front of the passive section 204. The laser 200 may also include a distributed Bragg reflector section 208 aligned with and located behind the active section 202, such that the active section 202 is sandwiched between the passive section 204 and the distributed Bragg reflector section 208.

[0040] The active section 202 may include one or more distributed feedback grating sections, each of which has a distributed feedback grating, such as two distributed feedback grating sections 210 and 212 separated by a phase shift 214, for example... Figure 2 As shown in the example, the total length of the active section 202 can range from 40 micrometers to 120 micrometers. For example, the total length of the active section 202 can range from 40 micrometers to 70 micrometers for 160 GHz operation or from 70 micrometers to 120 micrometers for 100 GHz operation. The two distributed feedback grating sections 210 and 212 can have the same or different lengths. In the example, the length of each of the distributed feedback grating sections is 25 micrometers. The grating intensity κ of each of the distributed feedback grating sections 210 and 212 can be approximately 513 cm⁻¹. -1 Or the grating intensity κ can be from 250cm -1 Up to 530cm -1 Within the range or from 480cm -1 Up to 550cm -1Within or elsewhere. Alternatively or additionally, the Bragg wavelength of each of the distributed feedback grating sections 210, 212 may be approximately 1.2913676 micrometers. More generally, each of the distributed feedback grating sections 210, 212 may have a Bragg wavelength in the range of 0 nanometers to 6 nanometers longer than the center wavelength of the reflection profile of the distributed Bragg reflector section 208. Alternatively or additionally, each of the distributed feedback grating sections 210, 212 may have a Bragg wavelength in the range of plus or minus 2 nanometers relative to the wavelength at which the reflection profile of the distributed Bragg reflector section 208 is 1 dB lower than the peak of the reflection profile. The phase shift 214 may be approximately 9.545 degrees or other suitable phase shifts that cause the laser mode to align with the longer wavelength edge of the distributed Bragg reflector section 208.

[0041] The passive segment 204 may include a passive waveguide 216 and a phase shifter 218. The length of the passive waveguide 216 may be approximately 130 micrometers, or may be in the range of 110 to 150 micrometers, or in the range of 80 to 170 micrometers, or in other ranges. The phase shifter 218 may be approximately 57 degrees, or in the range of 0 to 180 degrees, or in other ranges.

[0042] The reflectivity of the low-reflectivity mirror 206 can be 9% or less, 7% or less, or even 5% or less, such as 4%, 3%, 2%, 1.4%, 1%, or other reflectivities. In some embodiments, the reflectivity of the low-reflectivity mirror 206 is in the range of 0.5% to 15% or in the range of 3% to 8%. The front portion of the low-reflectivity mirror 206 and the distributed feedback grating 210 can be formed into an etalon in the laser 200.

[0043] The distributed Bragg reflector segment 208 may include a distributed Bragg reflector grating 220 and a phase shifter 222. In the example, the total length of the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220 may be 200 micrometers, or the length may be in the range of 100 micrometers to 200 micrometers or other ranges. The grating intensity κ of the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220 may be approximately 20 cm⁻¹. -1More generally, the grating intensity κ can be defined by the product κL, where L is the length of the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220; in some embodiments, κL can be in the range of approximately 0.4 to 1.4 or other ranges. Alternatively or additionally, the Bragg wavelength of the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220 can be approximately 1.2857000 micrometers. More generally, the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220 can have a Bragg wavelength in the range of 0 nanometers to 6 nanometers shorter than the Bragg wavelength of the distributed feedback grating segments 210, 212. Alternatively or additionally, the Bragg wavelength of the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220 may be defined relative to the Bragg wavelength of each of the distributed feedback segments 210, 212: each of the distributed feedback grating segments 210, 212 may have a Bragg wavelength in the range of plus or minus 2 nanometers relative to the wavelength in which the reflection profile of the distributed Bragg reflector segment 208 is lower than the peak of the reflection profile (e.g., the Bragg wavelength of the distributed Bragg reflector segment 208 / distributed Bragg reflector grating 220) by 1 dB. The phase shift 222 may be approximately 0 degrees, or in the range from 0 degrees to 180 degrees, or in other ranges.

[0044] Figure 3 This is a top front perspective view of another example laser 300 arranged according to at least one embodiment described herein, having strong light limitation caused by air. The laser 300 may include, be included in, or correspond to... Figure 1 and Figure 2 Either or both of the lasers 100 and 200.

[0045] Laser 300 can be implemented as a DR+R laser. Therefore, laser 300 may include an active section 302, a passive section 304 aligned with the active section 302, and a low-reflection mirror formed at the front of the passive section 304. For clarity, the low-reflection mirror is shown below... Figure 3The text is omitted. Laser 300 may further include a distributed Bragg reflector section 306 aligned with and located behind the active section 302, such that the active section 302 is sandwiched between the passive section 304 and the distributed Bragg reflector section 308. Each of the active section 302, passive section 304, low-reflection mirror, and distributed Bragg reflector section 306 of laser 300 may respectively include, be included in, or correspond to the active section 202, passive section 204, low-reflection mirror 206, and distributed Bragg reflector section 208 of laser 200. Active section 302 may, for example, include one or more distributed feedback gratings, and distributed Bragg reflector section 306 may, for example, include sections similar to... Figure 2 One or more distributed Bragg reflector gratings of the active section 202 and the distributed Bragg reflector section 208.

[0046] Each of the active section 302, the passive section 304, and the distributed Bragg reflector section 306 may include anodes 302A, 304A, and 306A, and cathodes 302B, 304B, and 306B. The anode 302A and cathode 302B of the active section 302 may respectively correspond to... Figure 1 The laser 300 has an anode 120 and a cathode 122. For example, current can be injected into the active section 302 of the laser 300 through the anode 302A, and the current can travel substantially laterally from the anode 302A through the active section 302 to the cathode 302B. Therefore, a modulation signal in the form of a modulation current injection signal can be applied through the anode 302A to the active section 302 to the cathode 302B to modulate the active section 302. Modulation of the active section 302 can modulate the cavity loss of the laser 300 and increase the relaxation oscillation frequency f of the laser 300. r .

[0047] A first bias signal can be applied to the passive section 304 up to the cathode 304B via the anode 304A to bias the passive section 304. A second bias signal can be applied to the distributed Bragg reflector section 306 up to the cathode 306B via the anode 306A to bias the distributed Bragg reflector section 306.

[0048] Alternatively or additionally, laser 300 may include a substrate 308 and a waveguide 310 spaced apart from the substrate 308 by an air gap 312. The substrate 308 and waveguide 310 may respectively include, be included in, or correspond to... Figure 1 The substrate 102 and waveguide 104. In the example, part or all of each of the active section 302, the passive section 304 and the distributed Bragg reflector section 306 may be formed in the waveguide 310 spaced apart from the substrate 308.

[0049] The substrate 308 may include indium phosphide or other suitable materials.

[0050] Waveguide 310 may include a gain medium 314, such as a multiple quantum well, which is vertically positioned within waveguide 310 between a first cladding member 316 (or lower cladding member) and a second cladding member 318 (or upper cladding member). The gain medium 314, the first cladding member 316, and the second cladding member 318 may respectively include, be included in, or correspond to... Figure 1 The gain medium 108, the first cover 110, and the second cover 112. For example, the thickness of each of the first cover 316 and the second cover 318 can be in the range of 0.05 micrometers to 0.15 micrometers.

[0051] Furthermore, the laser 300 may include multiple support members 320, a first current blocking structure 322 and a second current blocking structure 324, and a dielectric layer 326. Figure 3 Only some of the multiple support members 320 are visible in the image. The support member 320, the first current blocking structure 322, the second current blocking structure 324, and the dielectric layer 326 may respectively include, be included in, or correspond to the support member 320. Figure 1 The support member 320, the first current blocking structure 322, the second current blocking structure 324, and the dielectric layer 124 are provided. For example, the support member 320 may be integrally formed in the first current blocking structure 322 and the second current blocking structure 324, and / or the dielectric layer 326 may be formed on the waveguide 310.

[0052] Figures 4A to 4J The illustration shows a set of example epitaxial processing steps for forming a laser with strong light confinement caused by air, arranged according to at least one embodiment described herein. Figures 4A to 4J The laser formed may include, be included in, or correspond to Figure 1 and Figure 2 of Figures 1 to 3 Any one of the lasers 100, 200, and 300.

[0053] Reference Figure 4A At step 402, a material stack 404 may be constructed. The material stack 404 may include a substrate 406, a sacrificial layer 408, a first or lower cladding layer 410, a gain dielectric layer 412, and a second or upper cladding layer 414.

[0054] Substrate 406 may include indium phosphide or other suitable materials. Sacrificial layer 408 may include indium gallium aluminum arsenide (InGaAlAs), indium gallium arsenide (InGaAs), or other suitable materials. Lower cladding layer 410 may include indium phosphide. Gain dielectric layer 412 may include indium gallium arsenide indium phosphide (InGaAsP) multiple quantum wells or bulk layers, indium gallium aluminum arsenide multiple quantum wells or bulk layers, gallium indium nitride arsenide (GaInNAs) multiple quantum wells or bulk layers, or other suitable materials / configurations. Upper cladding layer 414 may include indium phosphide. One or more of the foregoing layers may be arranged along different longitudinal segments (e.g., along the longitudinal section) depending on the circumstances. Figure 4A The direction of page entry and exit in the longitudinal segment is doped or otherwise treated differently: whether a given longitudinal segment subsequently forms part of an active segment (e.g., active segment 302), a passive segment (e.g., passive segment 304), or a distributed Bragg reflector section (e.g., distributed Bragg reflector segment 306). Doping or other treatments may be implemented or constructed depending on the layers of the material stack 404 or after the entire material stack 404 has been constructed. For example, one or more distributed feedback gratings may be written in one or more of the lower cladding layer 410, the gain medium 412, or the upper cladding layer 414 in the longitudinal segment, which forms the active segment before subsequent layers are formed thereon.

[0055] Reference Figure 4B In step 416, a thick dielectric layer 418, such as a silicon dioxide layer with a thickness of approximately 0.4 to 1 micrometer, may be formed on the upper cladding layer 414. The thick dielectric layer 418 is formed at the location where the ridge structure will be formed in subsequent steps. The width of the thick dielectric layer 418 may be approximately 0.8 micrometers. The width of the thick dielectric layer 418 may be limited according to... Figures 4A to 4J The width of the gain medium 410 of the formed laser.

[0056] Reference Figure 4C In step 420, a thin dielectric layer 422, such as a silicon dioxide layer with a thickness of about 0.05 micrometers to 0.2 micrometers, can be formed on the upper cladding layer 414 and the thick dielectric layer 620.

[0057] Reference Figure 4D In step 424, photoresist 426 is selectively applied to the thin dielectric layer 422.

[0058] Reference Figure 4E At step 428, the material pile 404 is not... Figure 4DThe area covered by photoresist 426 is partially etched and the photoresist 426 is removed. In some embodiments, the etching may include two or more etching steps to partially etch through the material stack 404 to different depths in different regions. For example, one etching step may etch through the upper cladding layer 414 and the gain dielectric layer 412 in region 430. Another photoresist (not shown) may then be applied to region 432. Next, a second etching step may etch through the lower cladding layer 410 and the sacrificial layer 408 in region 434. After etching is complete, the photoresist is removed.

[0059] Reference Figure 4F In step 436, a current blocking structure 438 is formed in region 430. The current blocking structure 438 may include doped indium phosphide, such as n-doped indium phosphide. The current blocking structure 438 may include, be included in, or correspond to... Figure 1 or Figure 3 The second current blocking structures 118 and 324.

[0060] exist Figure 4F After step 436, Figures 4D to 4F At least some portions of one or more of steps 424, 428, and 436, such as photoresist, etching, and the formation of the current blocking structure 440, can be repeated on the opposite side of the thick dielectric layer 418 to form Figure 4G The waveguide 442 shown has current-blocking structures 438 and 440 on opposite sides. Furthermore, as... Figure 4G As shown, after waveguide 442 is formed, the thick dielectric layer 418 can be removed. Figure 4G As further illustrated, waveguide 442 includes a first cladding member 444 or lower cladding member formed by a lower cladding layer 410, a gain dielectric 446 formed by a gain dielectric layer 412, and a second cladding member 448 or upper cladding member formed by an upper cladding layer 414. The current blocking structure 440, waveguide 442, first cladding member 444, gain dielectric 44, and second cladding member 448 may respectively include, be included in, or correspond to... Figure 1 or Figure 3 The first current blocking structure 116, 322, waveguide 104, first cladding 110, 316, gain medium 108, 314, and second cladding 112, 318 are included.

[0061] Figure 4H include Figure 4G Top view, refer to Figure 4H At step 450, various dry etched holes 452 are formed by passing through a portion of the current blocking structures 438, 440 and a portion of the first cladding 444 into the remaining sacrificial layer 408 (only some of these dry etched holes are labeled for simplicity).

[0062] exist Figure 4H In the diagram, the dashed line intersects the dry-etched hole 452, representing the lateral extent of the first cladding 444 and the remaining sacrificial layer 408. The solid lines located between and parallel to the dashed lines represent the lateral extent of the gain dielectric 446 and the second cladding 448. Figure 4H It can be seen that the position of the dry etched hole 452 can be positioned to traverse and expose the remaining sacrificial layer 408, without traversing or exposing either the gain medium 446 or the second cover 448.

[0063] Reference Figure 4I At step 454, the remaining sacrificial layer 408 can be removed. Figure 4G For example, by exposing the remaining sacrificial layer 408 to a selective etchant through a dry etch hole 452 to etch away the remaining sacrificial layer 408 beneath the first cover 444 and forming Figure 4J The air gap 456 is shown in the example. Figure 4G and Figure 4H The entire structure can be immersed in a selective etchant to allow the selective etchant to enter the dry etch hole 452 and etch away the remaining sacrificial layer 408. Because the dry etch hole 452 does not traverse or expose the gain medium 446, it prevents the gain medium 446 from being exposed to the selective etchant.

[0064] Figure 4I Includes dashed arcs emanating from each of the dry-etched holes 452. The dashed arcs represent the etching path from the dry-etched hole 452 through the remaining sacrificial layer 408. Typically, a selective etchant can isotropically etch from the dry-etched hole 452 through the remaining sacrificial layer 408.

[0065] Reference Figure 4J At step 458, one or more anodes 460 and one or more cathodes 462 may be formed on the current blocking structures 438 and 440. For example, the first anode 460 and the first cathode 462 may be formed in a first longitudinal section that is or will be an active section, the second anode 460 and the second cathode 462 may be formed in a second longitudinal section that is or will be a passive section, and the third anode 460 and the third cathode 462 may be formed in a third longitudinal section that is or will be a distributed Bragg reflector section. Due to Figure 4J The cross-sectional view is taken from and based on Figures 4A to 4J The laser 464 is formed in a plane perpendicular to its length, therefore in Figure 4J Only one anode 460 and one cathode 462 are visible in the middle.

[0066] In some embodiments, the metallization forming the anode 460 and cathode 462 may partially or completely fill the dry etched hole 452 during the formation of the anode 460 and cathode 462.

[0067] According to Figures 4A to 4J The aforementioned steps simultaneously process multiple regions of the semiconductor wafer to form multiple lasers 464 in the wafer. Figure 4J Laser 464 can be isolated from a wafer, for example, by dicing or cutting. Alternatively or additionally, one or more low-reflection or HR mirrors can be formed on the cut surface of each laser in laser 464 to complete the formation of laser 464. For example, a low-reflection mirror can be formed on the front of the passive segment of each laser in laser 464.

[0068] Figure 5 This is a flowchart of an example method 500 for forming a laser according to at least one embodiment described herein. Specifically, method 500 can form a laser having strong light confinement caused by air. Method 500 may include one or more of blocks 502, 504, 506, 508, or 510. The method may begin at block 502.

[0069] At block 502, method 500 may include depositing a sacrificial layer on the substrate. Block 502 may, for example, serve as... Figure 4A This is part of step 402. Box 502 can be followed by box 504.

[0070] At block 504, method 500 may include forming a waveguide on the sacrificial layer. The waveguide may include a first cladding (or lower cladding), a second cladding (or upper cladding), and a gain medium located between the first cladding and the second cladding. Block 504 may serve as... Figure 4A This is performed as part of step 402. For example, as part of step 402, it involves establishing... Figure 4A A portion of the material stack 404, forming a waveguide on the sacrificial layer at frame 504 may include: depositing a first cladding layer including a first cladding member on the sacrificial layer; depositing a gain dielectric layer including a gain dielectric on the first cladding layer; and depositing a second cladding layer including a second cladding member on the gain dielectric layer.

[0071] In some embodiments, depositing a first coating layer on the sacrificial layer includes depositing a first coating layer on the sacrificial layer with a thickness ranging from 0.05 micrometers to 0.15 micrometers. Alternatively or additionally, depositing a second coating layer on the gain dielectric layer includes depositing a second coating layer on the gain dielectric layer with a thickness ranging from 0.05 micrometers to 0.15 micrometers.

[0072] Alternatively or additionally, forming a waveguide at block 504 may include Figures 4D to 4F The waveguide may be formed by vertically etching through the second cladding layer, the gain dielectric layer, the first cladding layer, and the sacrificial layer to the substrate in a first region of a material stack comprising a substrate, a sacrificial layer, a first cladding layer, a gain dielectric layer, and a second cladding layer to the substrate. Forming the waveguide may also include vertically etching through the second cladding layer, the gain dielectric layer, the first cladding layer, and the sacrificial layer to the first cladding layer in a second region of the material stack adjacent to the first region to form a first lateral boundary of the second cladding layer and the gain dielectric layer to the first cladding layer. Forming the waveguide may also include vertically etching through the second cladding layer and the gain dielectric layer to the first cladding layer in a third region of the material stack spaced between the first and second regions to form a second lateral boundary of the first cladding layer. Forming the waveguide may also include vertically etching through the second cladding layer, the gain dielectric layer, the first cladding layer, and the sacrificial layer to the substrate in a fourth region of the material stack adjacent to the third region to form a second lateral boundary of the second cladding layer and the gain dielectric layer to the first cladding layer. In these and other embodiments, the first side of the waveguide includes a first lateral boundary of the first cladding and a first lateral boundary of the second cladding and the gain medium; the second side of the waveguide includes a second lateral boundary of the first cladding and a second lateral boundary of the second cladding and the gain medium; and a first distance between the first lateral boundary of the first cladding and the second lateral boundary is greater than a second distance between the first lateral boundary of the second cladding and the gain medium and the second lateral boundary.

[0073] Box 504 can be followed by box 506.

[0074] At block 506, method 500 may include forming a first current-blocking structure laterally adjacent to a first side of the waveguide. Block 506 may include or be included in... Figure 4F Step 436. Box 506 can be followed by box 508.

[0075] At block 508, method 500 may include forming a second current-blocking structure laterally adjacent to a second side of the waveguide, the second side of the waveguide being opposite to the first side of the waveguide. Block 508 may be followed by block 510.

[0076] At block 510, the method may include forming an air gap between the substrate and the waveguide by selectively etching the sacrificial layer through a hole passing through a corresponding one of the first and second current blocking structures up to the sacrificial layer. Figure 4I Step 454.

[0077] Method 500 may further include dry etching the holes vertically through one of the first and second current blocking structures up to the sacrificial layer into materials that traverse the sacrificial layer but not the gain dielectric. In some embodiments, each hole in the vertical horizontal plane of the gain dielectric and the second cladding is completely defined by one of the first and second current blocking structures such that no hole traverses the material of the gain dielectric or the second cladding.

[0078] Method 500 may be modified, added to, or omitted without departing from the scope of this disclosure. For example, the operations of method 500 may be performed in a different order. Additionally or alternatively, two or more operations may be performed simultaneously. Furthermore, the operations and actions outlined are provided as examples only, and some operations and actions may be optional, may be combined into fewer operations and actions, or may be extended to additional operations and actions without departing from the essence of the described embodiments.

[0079] Figure 6 A simulated S21 response as a function of modulation frequency (Mod.Freq.) of an example laser arranged according to at least one embodiment described herein is shown. The laser may have strong light confinement caused by air and may have, for example, regarding Figure 2 and Figure 3 The disclosed DR+R cavity design (hereinafter referred to as a strongly optically confined DR+R laser) is shown. The horizontal axis represents the modulation frequency in GHz. The vertical axis represents the amplitude modulation (AM) response (resp.) in dBmW / mA. Curve 612 simulates the sum of contributions from all modes of the strongly optically confined DR+R laser. Curve 606 simulates the contribution of the dominant laser mode of the DR+R laser. Curve 610 simulates the contribution of the strongest sidemode of the DR+R laser, which is the main contribution of the photon-photon resonance effect. The remaining curves 602, 604, and 608 simulate the contributions of other weaker sidemodes of the DR+R laser. As can be seen from curve 612, the laser with strong optical confinement caused by air and the DR+R laser cavity design has a simulated 3-dB bandwidth greater than 160 GHz.

[0080] Figure 7 A simulated optical mode in the vertical direction is shown for an example laser with strong optical confinement caused by air, arranged according to at least one embodiment described herein. The laser may also have a DR+R laser cavity design. Figure 7 The cross-section of the multiple quantum wells or gain medium passing through the laser is marked with 702. Figure 7In the diagram, the vertical axis represents thickness in micrometers, while the horizontal axis represents the intensity profile of the light mode in arbitrary units. For example... Figure 7 As shown, the optical mode is essentially vertically confined within multiple quantum wells.

[0081] Figure 8 A simulated optical limitation as a function of the air gap thickness is shown for an example laser arranged according to at least one embodiment described herein, exhibiting strong optical limitation caused by air. The laser may also have a DR+R laser cavity design. Figure 8 Specifically simulated the vertical or horizontal light confinement of the laser. The light confinement is along... Figure 8 The vertical axis, and the air thickness along the horizontal axis in micrometers. Figure 8 The air thickness in this context refers to the thickness of the corresponding air gap between the laser's substrate and its waveguide. Figure 8 In the simulation, it is assumed that the first and second cladding elements, located above and below the corresponding gain medium of the waveguide, each have a thickness of 0.1 micrometers. From Figure 8 It can be seen that the vertical light confinement increases significantly when the air gap thickness increases from 0.2 μm to 0.3 μm. Therefore, in some embodiments described herein, the thickness of the air gap located between the substrate and the waveguide, and more specifically between the first cladding or lower cladding of the substrate and the waveguide, can be at least 0.3 μm. Furthermore, the vertical light confinement for an air gap thickness of 0.4 μm is almost twice that for an air gap thickness of 0 μm (e.g., no air gap).

[0082] Unless the specific arrangements described herein are mutually exclusive, the various implementations described herein can be combined, in whole or in part, to enhance system functionality or produce complementary functions. Similarly, aspects of the implementations can be implemented in independent arrangements. Therefore, the above description is given by way of example only, and detailed modifications can be made within the scope of this invention.

[0083] Regarding the use of substantially any plural or singular terms herein, those skilled in the art can convert plural to singular or vice versa depending on the context or application. For clarity, various singular / plural transformations may be explicitly stated herein. Unless otherwise stated, elements in singular form are not intended to mean "one and only one," but rather "one or more." Furthermore, whether or not such disclosure is explicitly stated in the foregoing description, nothing disclosed herein is intended to be exclusive to the public.

[0084] Generally, terms used herein, and especially in the appended claims (e.g., the body of the appended claims), are intended to be “open” terms (e.g., the term “comprising” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “including” should be interpreted as “including but not limited to,” etc.). Furthermore, in the use of idiomatic expressions such as “at least one of A, B, and C,” this structure is generally intended to make it clear to those skilled in the art that the idiomatic expression (a system having at least one of A, B, and C) will include, but is not limited to, systems having A alone, having B alone, having C alone, having A and B together, having A and C together, having B and C together, or having A, B, and C together, etc.). Similarly, phrases containing two or more alternative terms, whether in the specification, claims, or drawings, should be understood to include one of the terms, either of the terms, or both of the terms. For example, the phrase “A or B” will be understood to include the possibility of “A” or “B” or “A and B.”

[0085] The invention may be practiced in other specific forms without departing from the spirit or essential characteristics thereof. The described embodiments are to be considered in all respects illustrative rather than restrictive. Therefore, the scope of the invention is indicated by the appended claims rather than the foregoing description. All changes falling within the meaning and scope of equivalent substitutions of the claims should be included within their scope.

Claims

1. A laser, comprising: Substrate; A first covering element, which is spaced apart from the substrate by an air gap, wherein the thickness of the first covering element in the vertical direction is in the range of 0.05 micrometers to 0.15 micrometers; A gain medium is disposed on the first covering material opposite to the air gap; A second covering element, disposed opposite to the first covering element on the gain medium, wherein the thickness of the second covering element in the vertical direction is in the range of 0.05 micrometers to 0.15 micrometers; and A plurality of support members are coupled to each of the substrate, the first cover, the gain medium, and the second cover to hold the first cover, the gain medium, and the second cover spaced apart from the substrate.

2. The laser according to claim 1, further comprising: A first current blocking structure is positioned laterally adjacent to a first side portion of the first cover, the gain medium, and the second cover; as well as A second current blocking structure is positioned laterally adjacent to the first cover, the gain medium, and the second side portion of the second cover.

3. The laser according to claim 2, wherein, The plurality of support members are integrally formed in the first current blocking structure and the second current blocking structure.

4. The laser of claim 2 further includes an anode formed on the first current blocking structure and a cathode formed on the second current blocking structure to laterally inject current through the gain medium.

5. The laser according to claim 1, wherein: The first cladding element, the gain dielectric, and the second cladding element form a waveguide; The waveguide includes an active section, a passive section aligned with the active section, and a low-reflection mirror formed at the front of the passive section.

6. The laser according to claim 5, wherein, The active section includes a distributed feedback grating.

7. The laser according to claim 6, wherein, The waveguide also includes a distributed Bragg reflector section that is aligned with the active section and located behind the active section.

8. The laser according to claim 5, wherein, The low-reflectivity mirror has a reflectivity of 15% or less.

9. The laser according to claim 8, wherein, The low-reflectivity mirror has a reflectivity in the range of 3% to 8%.

10. The laser according to claim 1, wherein, The thickness of the air gap between the substrate and the first covering is at least 0.3 micrometers.

11. A laser, comprising: Substrate; A waveguide spaced apart from the substrate by an air gap, wherein the waveguide comprises: Distributed feedback active section; Passive sections that are in a straight line with the active section of the distributed feedback; and A distributed Bragg reflector section aligned with the active distributed feedback section, the active distributed feedback section located between the passive section and the distributed Bragg reflector section; and A low-reflectivity mirror is formed at the front of the passive section of the waveguide.

12. The laser according to claim 11, wherein, The low-reflectivity mirror has a reflectivity in the range of 3% to 8%.

13. The laser according to claim 11, wherein, The waveguide comprises in each of the distributed feedback active section, the passive section, and the distributed Bragg reflector section: A first covering element, wherein the first covering element is spaced apart from the substrate by the air gap; A gain medium, wherein the gain medium is disposed on the first covering member opposite to the air gap; and A second covering element is disposed on the gain medium in the opposite manner to the first covering element.

14. The laser according to claim 13, wherein: The thickness of the first covering in the vertical direction is in the range of 0.05 micrometers to 0.15 micrometers; and The thickness of the second covering in the vertical direction is in the range of 0.05 micrometers to 0.15 micrometers.

15. The laser of claim 11, further comprising a plurality of supports coupled to each of the substrate and the waveguide to support the waveguide spaced apart from the substrate.

16. The laser according to claim 11, wherein, The thickness of the air gap between the substrate and the waveguide is at least 0.3 micrometers.

17. A method of forming a laser, the method comprising: Deposit a sacrificial layer on the substrate; A waveguide is formed on the sacrificial layer, the waveguide including a first cladding and a second cladding, and a gain dielectric located between the first cladding and the second cladding; A first current blocking structure is formed that is laterally adjacent to the first side of the waveguide; A second current blocking structure is formed laterally adjacent to a second side portion of the waveguide, the second side portion of the waveguide being opposite to the first side portion of the waveguide; and An air gap is formed between the substrate and the waveguide by selectively etching the sacrificial layer through a hole passing through one of the first and second current blocking structures to the sacrificial layer.

18. The method according to claim 17, wherein, Forming the waveguide on the sacrificial layer includes: A first covering layer comprising the first covering element is deposited on the sacrificial layer; Deposit a gain dielectric layer comprising the gain dielectric on the first coating layer; and A second cladding layer comprising the second cladding element is deposited on the gain dielectric layer.

19. The method according to claim 18, wherein, At least one of the following: Depositing the first coating layer on the sacrificial layer includes depositing a first coating layer on the sacrificial layer with a thickness ranging from 0.05 micrometers to 0.15 micrometers; or Depositing the second coating layer on the gain dielectric layer includes depositing a second coating layer on the gain dielectric layer with a thickness ranging from 0.05 micrometers to 0.15 micrometers.

20. The method of claim 17, further comprising dry etching the hole vertically through one of the first current blocking structure and the second current blocking structure up to the sacrificial layer into a material that traverses the sacrificial layer but not the gain medium.

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