Semiconductor optical frequency comb laser and preparation method thereof

Abstract

The invention provides a semiconductor optical frequency comb laser and a preparation method, and relates to the technical field of semiconductor lasers. The semiconductor optical frequency comb laser comprises at least one first ridge region and at least one second ridge region. Under the condition that the sum of the number of the first ridge strip regions and the number of the second ridge strip regions is greater than or equal to 3, the first ridge strip regions and the second ridge strip regions are alternately coupled and connected in series; the width of each second ridge region is smaller than that of each first ridge region; wherein the at least one first ridge region is used for providing gain for a light beam; at least one second ridge region for suppressing a high order mode in the gained light beam; and regulating and controlling the nonlinear effect of the gain medium by controlling the carrier concentration of the gain medium in each second ridge region so as to generate the frequency modulation mode locking optical frequency comb.

Description

Technical Field

[0001] The present disclosure relates to the technical field of semiconductor lasers, and more specifically, to a semiconductor optical frequency comb laser and a preparation method thereof. Background Art

[0002] Pulse Mode-Locked Optical Frequency Comb is a laser that generates a series of ultrashort optical pulses with equal time intervals through a mode-locking mechanism. These pulses appear as a periodic sequence in the time domain and as a series of equally spaced discrete frequency components in the frequency domain, forming a structure similar to the teeth of a comb. It has high coherence and wide frequency coverage and can be widely used in precision measurement, optical communication, spectroscopy and other fields. However, the existing mode-locked laser system has a complex structure, requires a complex feedback control system and high-precision components, and has a high preparation cost, making it difficult to meet the needs of large-scale production. Summary of the invention

[0003] In view of this, the present disclosure provides a semiconductor optical frequency comb laser and a preparation method thereof.

[0004] On the one hand, the present disclosure provides a semiconductor optical frequency comb laser comprising: at least one first ridge region and at least one second ridge region; when the sum of the number of the first ridge regions and the number of the second ridge regions is greater than or equal to 3, the first ridge regions and the second ridge regions are alternately coupled in series; the width of each second ridge region is smaller than the width of each first ridge region; wherein at least one first ridge region is used to provide gain for the light beam; at least one second ridge region is used to suppress high-order modes in the light beam after gain; and the nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each second ridge region to generate a frequency-modulated mode-locked optical frequency comb.

[0005] According to an embodiment of the present disclosure, the nonlinear effect of the gain medium is regulated, including: controlling the carrier concentration of the gain medium in at least one second ridge region to stimulate the spatial hole burning effect to produce multiple longitudinal modes; and stimulating at least one second ridge region to produce a four-wave mixing effect to regulate the frequency interval between the multiple longitudinal modes.

[0006] According to an embodiment of the present disclosure, regulating the nonlinear effect of the gain medium also includes: a single electrode, at least one first ridge region and at least one second ridge region sharing the single electrode; by controlling the positive current injected into the single electrode to be greater than a threshold value, the gain medium of at least one second ridge region undergoes optical saturation to regulate the nonlinear effect of the gain medium.

[0007] According to an embodiment of the present disclosure, regulating the nonlinear effect of the gain medium also includes: injecting a positive current into a single electrode; traversing the range of the injected positive current with a preset step size to determine the operating current of the frequency-modulated mode-locked optical frequency comb.

[0008] According to an embodiment of the present disclosure, the semiconductor optical frequency comb laser further includes: at least one transition region, each first ridge region and each second ridge region are alternately coupled in series through a transition region; and is used to couple the light beam after gain in the first ridge region to the second ridge region adjacent to the first ridge region.

[0009] According to an embodiment of the present disclosure, each transition region includes a first end and a second end; wherein the first end is connected to each first ridge region correspondingly; the second end is connected to each second ridge region correspondingly; the width of the first end is the same as the width of each first ridge region, and the width of the second end is the same as the width of each second ridge region.

[0010] According to an embodiment of the present disclosure, the total length of at least one first ridge region is 50%-60% of the remaining cavity length of the semiconductor optical frequency comb laser cavity after subtracting the total length of at least one transition region.

[0011] According to an embodiment of the present disclosure, the total length of at least one second ridge region is 40%-50% of the remaining cavity length of the semiconductor optical frequency comb laser cavity after subtracting the total length of at least one transition region.

[0012] According to an embodiment of the present disclosure, the material of the semiconductor optical frequency comb laser includes a III-V group compound semiconductor.

[0013] The second aspect of the present disclosure provides a method for preparing a semiconductor optical frequency comb laser, comprising: preparing an epitaxial wafer; growing a protective layer on the epitaxial wafer; performing photolithography and etching on the protective layer to prepare at least one first ridge region and at least one second ridge region, wherein, when the sum of the number of the first ridge regions and the number of the second ridge regions is greater than or equal to 3, the first ridge regions and the second ridge regions are alternately coupled in series; the width of each second ridge region is smaller than the width of each first ridge region; wherein at least one first ridge region is used to provide gain for the light beam; at least one second ridge region is used to suppress high-order modes in the light beam after gain; and the nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each second ridge region to generate a frequency-modulated mode-locked optical frequency comb; growing an insulating layer on the surface of the epitaxial wafer containing at least one first ridge region and at least one second ridge region; photolithography and etching an injection window on the insulating layer; growing a P-face metal on the surface of the epitaxial wafer containing the injection window; and growing an N-face electrode on the surface of the epitaxial wafer away from the P-face metal to obtain a semiconductor optical frequency comb laser.

[0014] The semiconductor optical frequency comb laser provided in the embodiments of the present disclosure has at least the following beneficial effects:

[0015] By arranging each second ridge area and the first ridge area corresponding to each second ridge area to be alternately coupled in series to form a single-stage structure, the structure is simple, does not require complex external components, and can meet large-scale production requirements.

[0016] By setting a second ridge region corresponding to the first ridge region, a high nonlinear effect can be achieved to output a frequency-modulated mode-locked optical frequency comb, and when a positive current is injected, a mode-locked state can be achieved within a certain current range, and a frequency-modulated periodic waveform can be output in the time domain.

[0017] The method for preparing the semiconductor optical frequency comb laser disclosed in the present invention has a simple preparation process, does not require secondary epitaxy, and reduces the manufacturing cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0019] Figure 1 The structure diagram of the semiconductor optical frequency comb laser according to the embodiment of the present disclosure is schematically shown;

[0020] Figure 2 The schematic diagram of the epitaxial structure of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is shown schematically;

[0021] Figure 3 A flow chart of a method for preparing a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown;

[0022] Figure 4 Schematically shows a time domain diagram of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure;

[0023] Figure 5 Schematically shows a frequency domain diagram of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure;

[0024] Figure 6 Schematically shows a phase diagram of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure;

[0025] Figure 7 A diagram schematically shows the relationship between the length and transmittance of the transition region of the semiconductor optical frequency comb laser according to an embodiment of the present disclosure;

[0026] Figure 8 The schematic diagram of energy transfer distribution of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown;

[0027] Fig. 9 The diagram schematically shows the repetition rate of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0028] Hereinafter, embodiments of the present disclosure will be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the present disclosure. In the following detailed description, for ease of explanation, many specific details are set forth to provide a comprehensive understanding of the embodiments of the present disclosure. However, it is apparent that one or more embodiments may also be implemented without these specific details. In addition, in the following description, descriptions of known systems and technologies are omitted to avoid unnecessary confusion of the concepts of the present disclosure.

[0029] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0030] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0031] When using expressions such as "at least one of A, B, and C, etc.", they should generally be interpreted according to the meaning of the expression commonly understood by those skilled in the art (for example, "a system having at least one of A, B, and C" should include but is not limited to a system having A alone, B alone, C alone, A and B, A and C, B and C, and / or A, B, C, etc.).

[0032] In order to achieve stable ultrashort pulse output, the existing pulse mode-locked optical frequency comb usually sets up an electrical isolation structure to separate the gain region from the saturated absorption region to ensure that there is no unnecessary interaction between the two regions. In this system, a positive bias current is injected into the gain region to provide a sufficient number of inversion particles so that the laser can be started and maintained; a reverse bias current is injected into the saturated absorption region to adjust its transmittance characteristics, help lock the mode interval and stabilize the pulse sequence.

[0033] However, the introduction of additional electrical isolation structures and dual current source control systems increases the complexity of the system, which not only increases the manufacturing cost, but also increases the number of failure points due to the increase in components. At the same time, since there are multiple variables that need to be precisely controlled, any slight change may cause fluctuations in the output pulse characteristics, affecting the long-term stability and repeatability of the optical frequency comb.

[0034] Based on this, the embodiments of the present disclosure provide a frequency modulated mode-locked optical frequency comb, which has a simple structure and does not require complex external components by setting a single-stage structure, and can meet the needs of large-scale production. And by controlling the second ridge region to produce a high nonlinear effect, a frequency modulated mode-locked optical frequency comb with good stability is generated, and high-order modes are filtered out to output a stable fundamental mode.

[0035] In the embodiments of the present disclosure, when the injection current is higher than the threshold current, resonance is formed and a spatial hole burning effect is generated, resulting in edge mode competition and multi-mode output. When the intracavity power is large enough, due to the increase in nonlinear effects, the four-wave mixing effect is stimulated, which can have an effect similar to light injection locking, so that the multi-mode output becomes equidistant comb teeth. The population grating caused mainly by the spatial hole burning effect will cause the modulation of the number of carrier particles and then cause the third-order nonlinear effect, thereby changing the gain and refractive index, so that the multi-mode output in the frequency domain becomes equidistant comb teeth, but the phase of the equidistant comb teeth in the frequency domain is chaotic.

[0036] Both amplitude and frequency can cause equidistant comb teeth. Amplitude modulation is to modulate the output power of the laser by changing the amplitude of the injected current; frequency modulation is to modulate the output frequency of the laser by changing the frequency of the injected current.

[0037] However, since the population pulsation is mainly affected by the amplitude modulated population inversion and optical parametric gain, for fast gain media (the carrier gain time T1 is related to the intracavity light field intensity, therefore, by increasing the intracavity light field intensity, the quantum well medium can behave like a fast gain medium), it manifests as parametric loss in a larger frequency range. According to the principle of maximum laser emission, it can be determined that the amplitude modulation is suppressed and manifests as frequency modulation.

[0038] At the same time, dispersion and gain curvature can affect the phase-locking mechanism, causing the phase to exhibit a chirped nature, that is, the derivative of the phase is linear over time.

[0039] Figure 1 The structure of the semiconductor optical frequency comb laser according to the embodiment of the present disclosure is schematically shown.

[0040] like Figure 1 As shown, the present disclosure provides a semiconductor optical frequency comb laser including: at least one first ridge region 1 and at least one second ridge region 2.

[0041] When the sum of the number of first ridge stripe regions 1 and the number of second ridge stripe regions 2 is greater than or equal to 3, the first ridge stripe regions 1 and the second ridge stripe regions 2 are alternately coupled in series; the width of each second ridge stripe region is smaller than the width of each first ridge stripe region.

[0042] Wherein, at least one first ridge region 1 is used to provide gain for the light beam.

[0043] At least one second ridge region 2 is used to suppress high-order modes in the gained light beam; and the nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each second ridge region to generate a frequency-modulated mode-locked optical frequency comb.

[0044] In the embodiments of the present disclosure, by setting at least one first ridge region, the energy density is small, the light saturation effect is weak, and high gain can be provided, and high light field intensity and intracavity resonant light power can be generated. The width of the second ridge region is set to be smaller than the first ridge region to ensure that only the fundamental mode can propagate therein, effectively suppressing the high-order mode, reducing multi-transverse mode interference, and improving the beam quality and stability. At the same time, the energy density of the second ridge region is small, the light saturation effect is strong, and it has a high nonlinear effect.

[0045] By adopting a design in which multiple first ridge regions and second ridge regions are alternately coupled in series, the overall structure is simplified, the use of complex components is reduced, and the manufacturing and maintenance costs are effectively reduced. At the same time, by precisely controlling the carrier concentration of the gain medium in each second ridge region, the nonlinear effect of the gain medium can be optimized, ensuring high stability of the frequency interval and low phase noise.

[0046] Among them, the number of the first ridge region and the second ridge region can be set as needed, and setting multiple first ridge regions can provide higher gain for the light beam. Setting multiple second ridge regions can better filter out high-order modes and output a stable fundamental mode, while improving nonlinear effects and generating a stable frequency-modulated mode-locked optical frequency comb. When the total number of the first ridge region and the second ridge region is two, the first ridge region and the second ridge region are directly coupled and connected. When the total number of the first ridge region and the second ridge region is greater than or equal to 3, the first ridge region and the second ridge region are alternately coupled in series.

[0047] In some possible embodiments, the semiconductor optical frequency comb laser includes two first ridge regions 1 and one second ridge region 2, wherein the two first ridge regions are located at two ends of the second ridge region and are alternately coupled to the second ridge region.

[0048] On the basis of the above embodiments, the nonlinear effect of the gain medium is regulated, including: controlling the carrier concentration of the gain medium in at least one second ridge region to stimulate the spatial hole burning effect to produce multiple longitudinal modes; and stimulating at least one second ridge region to produce a four-wave mixing effect to regulate the frequency interval between the multiple longitudinal modes.

[0049] By precisely controlling the carrier concentration of the gain medium in the second ridge region, effective hole burning can be formed at specific locations. These hole burnings suppress the gain of higher-order modes, so that only those longitudinal modes that can obtain sufficient gain at the hole burning location can oscillate stably. Therefore, in the end, only a few specific longitudinal modes can exist and oscillate stably, forming multiple longitudinal modes. At high power density, the four-wave mixing effect can be stimulated, which will promote phase locking between different longitudinal modes, so that the frequency difference between adjacent longitudinal modes remains constant.

[0050] On the basis of the above-mentioned embodiments, the nonlinear effect of the gain medium is regulated, and further includes: a single electrode, at least one first ridge region and at least one second ridge region share the single electrode; by controlling the positive current injected into the single electrode to be greater than a threshold value, the gain medium of at least one second ridge region undergoes optical saturation to regulate the nonlinear effect of the gain medium.

[0051] By controlling the positive current injected into a single electrode to be greater than a threshold, the gain medium in the second ridge region can be ensured to enter a light-saturated state, and the nonlinear effect of the gain medium can be effectively regulated, thereby ensuring the stable oscillation of multiple longitudinal modes and the high consistency of the frequency interval. Specifically, when the injected current exceeds a certain threshold, the carrier concentration in the gain medium increases sharply, resulting in a significant light-saturation effect. In addition, by adopting a single-electrode design, the number of electrodes that need to be independently controlled is reduced, further simplifying the system and reducing costs.

[0052] On the basis of the above embodiment, regulating the nonlinear effect of the gain medium also includes: injecting a positive current into the single electrode; traversing the range of the injected positive current with a preset step size to determine the operating current of the frequency-modulated mode-locked optical frequency comb.

[0053] In the embodiments of the present disclosure, by traversing the range of injected positive current and adjusting it step by step with a preset step size, the optimal operating current of the frequency modulation mode-locked optical frequency comb can be accurately determined. Under this operating current, the optical frequency comb exhibits stable frequency modulation mode-locked characteristics, with high frequency interval consistency and low phase noise.

[0054] According to an embodiment of the present disclosure, the semiconductor optical frequency comb laser further includes: at least one transition region 3, each first ridge region 1 and each second ridge region 2 are alternately coupled in series through a transition region 3; and is used to couple the light beam after gain in the first ridge region to the second ridge region adjacent to the first ridge region.

[0055] In the embodiments of the present disclosure, by providing at least one transition region, the light beam can be efficiently coupled from the first ridge region to the second ridge region, reducing scattering and reflection and lowering power loss. Avoiding direct connection between the first ridge region and the second ridge region will lead to increased power loss, transverse mode mismatch, and inability to effectively capture transverse mode energy, which seriously affects the transmission quality of the optical signal and system performance.

[0056] On the basis of the above embodiment, each transition region includes a first end and a second end; wherein the first end is connected to each first ridge region correspondingly; and the second end is connected to each second ridge region correspondingly.

[0057] The width of the first end is the same as the width of each first ridge region, and the width of the second end is the same as the width of each second ridge region.

[0058] In an embodiment of the present disclosure, by setting the first end width of the transition zone to be the same as the width of the first ridge zone, it is ensured that there is no sudden change in the light beam when entering the transition zone, thereby avoiding unnecessary scattering and reflection. The second end width of the transition zone is the same as the width of the second ridge zone, thereby ensuring that the light beam can propagate smoothly when entering the second ridge zone, thereby avoiding transverse mode mismatch. Inside the transition zone, the width gradually decreases from the first end to the second end, forming a smooth gradient structure, which can effectively guide the propagation path of the light beam and reduce energy loss in mode conversion. It should be noted that the length of each transition zone can be set as needed, and the longer the length, the more efficient the energy transfer.

[0059] According to an embodiment of the present disclosure, the total length of at least one first ridge region is 50%-60% of the remaining cavity length of the semiconductor optical frequency comb laser cavity after subtracting the total length of at least one transition region.

[0060] In the embodiments of the present disclosure, by accurately defining the proportion of the total length of the first ridge region, the mode field area corresponding to the first ridge region is effectively controlled, which can ensure that the laser operates in the best working state. And by controlling the mode field area, the threshold current of the laser can be adjusted to maintain it within a reasonable range, which helps to improve the output power of the laser, the quality and stability of the beam. At the same time, the longer first ridge region can reduce the average current injection density, reduce the risk of local overheating, and help provide system stability.

[0061] According to an embodiment of the present disclosure, the total length of at least one second ridge region is 40%-50% of the remaining cavity length of the semiconductor optical frequency comb laser cavity after subtracting the total length of at least one transition region.

[0062] In the embodiments of the present disclosure, the proportion of the second ridge region is precisely controlled so that the second ridge region maintains a high nonlinear effect and loss balance, and avoids the second ridge region being too long, which will affect the output power of the laser and increase the loss and energy consumption. If the second ridge region is too short, the high-order mode cannot be effectively filtered out, and the spatial hole burning effect and four-wave mixing effect are insufficient, and multi-longitudinal mode phase locking cannot be achieved.

[0063] According to the embodiments of the present disclosure, the material of the semiconductor optical frequency comb laser includes III-V compound semiconductors. The laser is integrally active, which is beneficial to compensate for the power loss caused by electrical isolation and etching of the surface grating and improve the power of the entire laser. The semiconductor epitaxial material has the advantages of a wide gain range and a low threshold current. At the same time, the electrical injection pumping method is convenient to use and easy to achieve high-precision control.

[0064] According to an embodiment of the present disclosure, a bias device is further included to generate a radio frequency signal, and the radio frequency signal is mixed with the light beam to stabilize the performance of the optical frequency comb.

[0065] Figure 2 A schematic diagram of the epitaxial structure of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is shown schematically.

[0066] Figure 3 The flowchart of the method for preparing a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown.

[0067] like Figure 2 and Figure 3 As shown, the second aspect of the present disclosure provides a method for preparing a semiconductor optical frequency comb laser, comprising:

[0068] Step 1: Prepare epitaxial wafer; Multiple epitaxial growth on substrate Buffer layer, Gradient layer, Cladding, Gradient layer, periodic unit, Gradient layer, Cladding, layer, Cladding, layer, Layer and The periodic unit includes a sequentially stacked Barrier layer, Quantum well layers and Barrier layer, the period number of the period unit is 5; UID means undoped.

[0069] Step 2: growing a silicon dioxide protective layer on the prepared epitaxial wafer;

[0070] Step three: perform multiple photolithography and etching processes on the protective layer to prepare at least one first ridge region and at least one second ridge region, wherein, when the sum of the number of the first ridge regions and the number of the second ridge regions is greater than or equal to 3, the first ridge regions and the second ridge regions are alternately coupled in series; the width of each second ridge region is smaller than the width of each first ridge region; wherein, at least one first ridge region is used to provide gain for the light beam; at least one second ridge region is used to suppress high-order modes in the gained light beam; and the nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each second ridge region to generate a frequency-modulated mode-locked optical frequency comb; the photoresist includes AZ703.

[0071] Step 4: After step 3, remove the remaining silicon dioxide, and re-grow a silicon dioxide insulating layer on the surface of the epitaxial wafer containing at least one first ridge region and at least one second ridge region;

[0072] Step 5: photolithographically etching a power injection window on the insulating layer to expose the epitaxial wafer under the insulating layer;

[0073] Step 6: Grow P-side metal on the surface of the epitaxial wafer containing the injection window, use photolithography and etch the metal to image the electrode to form a single electrode;

[0074] Step 7: After thinning and polishing the surface of the epitaxial wafer away from the P-side metal, an N-side electrode is grown on this surface.

[0075] Step 8: Coat high reflection film HR and anti-reflection film AR on both ends; then scribing and cleavage to obtain the semiconductor optical frequency comb laser.

[0076] In the embodiments of the present disclosure, the preparation method of the semiconductor optical frequency comb laser is simple, does not require secondary epitaxy and electron beam lithography, and can be achieved using ordinary optoelectronic processes, which can reduce production costs and meet large-scale production requirements.

[0077] Based on the above embodiment, the frequency modulated mode-locked optical frequency comb laser includes two first ridge regions 1 and one second ridge region 2, wherein the two first ridge regions 1 are located at both ends of the second ridge region 2, and the two first ridge regions 1 and one second ridge region 2 are alternately coupled in series through a transition region 3.

[0078] The etching depths of the first ridge region and the second ridge region may include 1.75 μm, but are not limited thereto.

[0079] The lengths of the two first ridge regions are L1=L3=460um, the length of the second ridge is L2=920um, the length of the transition region is L5=100um, the total cavity length is 2040um, the width of the first ridge is L4=10.4um, and the width of the second ridge is L4 / 4=2.6um.

[0080] The prepared frequency-modulated mode-locked optical frequency comb laser was fixed on a C-Mount heat sink and temperature control was used to control the temperature, and multiple performance characterization tests were performed.

[0081] After the test starts, a positive current is injected into a single electrode of a single-stage structure. The range of the injected positive current is 0-500mA. The injected current is scanned in 2mA steps. When the laser starts to lasing, it is recorded as the threshold current. The current is continued to increase. When the laser enters the mode-locked state, it is recorded as the mode-locked threshold current. The current is continued to increase, and the mode-locked state will disappear and reappear. The injection current range with mode-locked characteristics is the mode-locked characteristic working area. The frequency modulation characteristics of the optical frequency comb can be measured by the step heterodyne method to verify its characteristics of almost stability in the time domain, multi-mode lasing in the frequency domain, and phase chirp change.

[0082] Figure 4 The time domain diagram of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown.

[0083] Figure 5 The frequency domain diagram of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown.

[0084] Figure 6 The phase diagram of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown.

[0085] like Figure 4 As shown, the frequency modulated optical frequency comb of this embodiment exhibits obvious periodicity and sharp peaks in the time domain and has periodic stability.

[0086] like Figure 5 As shown in the figure, in the frequency domain, within the position range of 0 to about 6 mm, the frequency shows a linear increase trend, and the frequency increases evenly with the increase of the position; at a position of about 6 mm, the frequency shows an obvious mutation, and the frequency drops rapidly from close to 0.4 THz to close to -0.5 THz, and rises rapidly back to a value close to 0 THz in a short time; after 6 mm, the frequency shows a linear increase trend again. This shows that multiple longitudinal modes are output and the intervals between the multiple longitudinal modes are consistent.

[0087] like Figure 6 As shown, the phase changes linearly with the position, showing the chirp characteristic of the phase.

[0088] Figure 7The relationship between the length and transmittance of the transition region of the semiconductor optical frequency comb laser according to an embodiment of the present disclosure is schematically shown.

[0089] like Figure 7 As shown, the transmittance of the transition region can be regulated by controlling the length of the transition region, and the energy coupling from the first ridge region to the second ridge region can be better controlled to reduce the loss.

[0090] Figure 8 The energy transfer distribution diagram of the semiconductor optical frequency comb laser according to the embodiment of the present disclosure is schematically shown.

[0091] like Figure 8 As shown, the energy distribution diagram of the first ridge area and the second ridge area is given. Figure 8 It can be seen that the energy ratio of the first ridge region to the second ridge region is 3.2:1.

[0092] Fig. 9 The diagram schematically shows the repetition rate of a semiconductor optical frequency comb laser according to an embodiment of the present disclosure.

[0093] like Fig. 9 As shown, it is single-mode lasing with narrow line width, high frequency stability and low noise characteristics when the injection current is 0.7A.

[0094] Therefore, the semiconductor optical frequency comb laser of the embodiment of the present disclosure can output stable repetition rate, high power, simple process and low cost. When the laser is given enough anomalous dispersion compensation, pulses can be reproduced in the time domain, which further illustrates that the phase curve is a parabolic characteristic. Specifically, since the amplitude modulation will be suppressed, the frequency-locked laser cannot express time-domain pulses. The time-domain pulse requires the phase between the comb teeth to be equal, and the phase between the comb teeth of the frequency-locked laser chirps. Therefore, it is possible to add a section of anomalous dispersion fiber (i.e., phase chirp with opposite slope) to compensate, so that the phase between the comb teeth is equal and the pulse is reproduced.

[0095] At the same time, the changes in the injected current can be used to observe the changes in the repetition rate peak power, peak wavelength, and the quality of the spectral characteristics, and to judge the impact of temperature and carrier changes on the laser characteristics. When the laser is externally injected with an RF signal or light injection equal to the repetition rate, the locking mode characteristics and spectral characteristics can be adjusted to achieve excellent performance with a narrower repetition rate line width and a flatter spectrum.

[0096] It will be appreciated by those skilled in the art that the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways, even if such combinations and / or combinations are not explicitly described in the present disclosure. In particular, the features described in the various embodiments and / or claims of the present disclosure may be combined and / or combined in a variety of ways without departing from the spirit and teachings of the present disclosure. All of these combinations and / or combinations fall within the scope of the present disclosure.

[0097] The embodiments of the present disclosure are described above. However, these embodiments are only for illustrative purposes and are not intended to limit the scope of the present disclosure. Although the embodiments are described above separately, this does not mean that the measures in the various embodiments cannot be used in combination to advantage. The scope of the present disclosure is defined by the attached claims and their equivalents. Without departing from the scope of the present disclosure, those skilled in the art may make a variety of substitutions and modifications, which should all fall within the scope of the present disclosure.

Claims

1. A semiconductor optical frequency comb laser, characterized in that: include: at least one first ridge region and at least one second ridge region; When the sum of the number of the first ridge regions and the number of the second ridge regions is greater than or equal to 3, the first ridge regions and the second ridge regions are alternately coupled in series; the width of each of the second ridge regions is smaller than the width of each of the first ridge regions; Wherein, the at least one first ridge region is used to provide gain for the light beam; The at least one second ridge region is used to suppress high-order modes in the amplified light beam; as well as The nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each of the second ridge stripe regions to generate a frequency modulated mode-locked optical frequency comb.

2. The semiconductor optical frequency comb laser according to claim 1, characterized in that: The regulating the nonlinear effect of the gain medium comprises: Controlling the carrier concentration of the gain medium in the at least one second ridge region to stimulate a spatial hole burning effect to generate multiple longitudinal modes; and The at least one second ridge region is excited to generate a four-wave mixing effect to adjust the frequency interval between the multiple longitudinal modes.

3. The semiconductor optical frequency comb laser according to claim 2, characterized in that: Also includes: A single electrode, the at least one first ridge region and the at least one second ridge region share the single electrode; The nonlinear effect of the gain medium is regulated by controlling the positive current injected into the single electrode to be greater than a threshold value so that the gain medium in the at least one second ridge region undergoes optical saturation.

4. The semiconductor optical frequency comb laser according to claim 3, characterized in that: Also includes: injecting a positive current into the single electrode; The range of the injected positive current is traversed with a preset step size to determine the operating current of the frequency-modulated mode-locked optical frequency comb.

5. The semiconductor optical frequency comb laser according to claim 1, characterized in that: Also includes: At least one transition region, each of the first ridge regions and each of the second ridge regions are alternately coupled in series through one of the transition regions; The method is used to couple the light beam after being amplified by the first ridge region to the second ridge region adjacent to the first ridge region.

6. The semiconductor optical frequency comb laser according to claim 5, characterized in that: Each of said transition regions comprises a first end and a second end; Among them, the first end is connected to each of the first ridge regions correspondingly; the second end is connected to each of the second ridge regions correspondingly; the width of the first end is the same as the width of each of the first ridge regions, and the width of the second end is the same as the width of each of the second ridge regions.

7. The semiconductor optical frequency comb laser according to claim 1, characterized in that: The total length of the at least one first ridge region is 50%-60% of the remaining cavity length after the total length of the at least one transition region is subtracted from the cavity length of the semiconductor optical frequency comb laser.

8. The semiconductor optical frequency comb laser according to claim 7, characterized in that: The total length of the at least one second ridge region is 40%-50% of the remaining cavity length after the total length of the at least one transition region is subtracted from the cavity length of the semiconductor optical frequency comb laser.

9. The semiconductor optical frequency comb laser according to claim 1, characterized in that: The material of the semiconductor optical frequency comb laser includes III-V group compound semiconductor.

10. A method for preparing a semiconductor optical frequency comb laser, characterized in that: include: Preparation of epitaxial wafers; growing a protective layer on the epitaxial wafer; Performing photolithography and etching on the protective layer to prepare at least one first ridge region and at least one second ridge region, wherein, when the sum of the number of the first ridge regions and the number of the second ridge regions is greater than or equal to 3, the first ridge regions and the second ridge regions are alternately coupled in series; the width of each of the second ridge regions is smaller than the width of each of the first ridge regions; the at least one first ridge region is used to provide gain for the light beam; the at least one second ridge region is used to suppress high-order modes in the light beam after gain; and the nonlinear effect of the gain medium is regulated by controlling the carrier concentration of the gain medium in each of the second ridge regions to generate a frequency-modulated mode-locked optical frequency comb; Growing an insulating layer on the surface of the epitaxial wafer including the at least one first ridge stripe region and the at least one second ridge stripe region; Photolithographically etching a power injection window on the insulating layer; Growing a P-plane metal on the surface of the epitaxial wafer containing the injection window; An N-side electrode is grown on the surface of the epitaxial wafer away from the P-side metal to obtain the semiconductor optical frequency comb laser.

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