Semiconductor laser with adjustable time domain

Abstract

The invention relates to the technical field of semiconductor lasers, in particular to a semiconductor laser with an adjustable time domain. According to the time-domain-adjustable semiconductor laser, a mutual injection coupling region and a gain region are arranged on a semiconductor laser chip, the mutual injection coupling region comprises multiple sections of interval units, and the ratio of the length of a saturable absorber region to the length of the gain region in a resonant cavity is controlled by adjusting the absorption / gain characteristics of the interval units. And a plurality of pulse generation mechanisms are switched to adjust the pulse width. On the premise that the structural complexity of the semiconductor laser is reduced, large-range adjustment of laser pulses can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor lasers, and particularly relates to a semiconductor laser with adjustable time domain. Background Art

[0002] Ultra-short pulse lasers can release a large amount of energy in an extremely short time, which is of great significance for the interaction between laser and matter and for detecting the reaction process of substances in the microscopic field. It is an important means for studying ultrafast physical, chemical, and biological processes, and has broad application prospects in the fields of material processing, medical beauty, laser ranging, and radar. Lasers with different time scales have different effects on substances, and precisely controlling the pulse width of the laser is the key to achieving efficient and accurate applications. With the development of technology, tunable pulse lasers in the time domain will also play an important role in emerging fields such as quantum communication and quantum measurement.

[0003] Existing ultra-short pulse semiconductor lasers mostly adopt a single pulse generation mechanism, such as technologies like gain switching, mode locking, and Q-switching, which can only generate pulses with a single pulse width or achieve a small range of pulse width adjustment within a single time scale range. Another method to change the pulse width is to introduce a dispersion management module into the resonator structure for time domain control, such as inserting dispersion elements like gratings and prisms into the resonator cavity. However, the problems are as follows: This technical solution requires complex design and adjustment of the optical system, increasing the complexity and volume of the internal structure of the resonator cavity. In addition, this technical solution needs to control the dispersion of light through dispersion elements to achieve pulse width broadening or compression. Therefore, the dispersion adjustment ability of this technical solution depends on the structure of the dispersion elements themselves, resulting in a limited adjustment range. Therefore, how to reduce the complexity of the semiconductor laser structure while achieving a large range of adjustment of the laser pulse width has become an urgent problem to be solved. Summary of the Invention

[0004] In view of this, the present invention aims to provide a semiconductor laser with adjustable time domain, which can achieve a large range of adjustment of laser pulses on the premise of reducing the structural complexity of the semiconductor laser.

[0005] To achieve the above object, the technical solution of the present invention is realized as follows: The present invention provides a semiconductor laser with adjustable time domain. An injection-coupling region and a gain region are arranged on a semiconductor laser chip. The injection-coupling region includes multiple interval units, and by adjusting the absorption / gain characteristics of the interval units, the ratio of the length of the saturable absorber region in the resonator cavity to the length of the gain region is controlled, and multiple pulse generation mechanisms are switched to adjust the pulse width.

[0006] Furthermore, the mutual injection coupling region is made of a material with convertible bias voltage characteristics. The interval units are independently controlled by electrodes, and a bias voltage is applied to the interval units through the electrodes to adjust the gain / absorption characteristics of the interval units.

[0007] Furthermore, when a forward bias voltage is applied to the interval unit through the electrode, the interval unit is adjusted to have a gain characteristic, and the interval unit is added to the gain region.

[0008] Furthermore, when a reverse bias voltage is applied to the interval unit through the electrode, the interval unit is adjusted to have an absorption characteristic, and the interval unit is set as the saturable absorber region.

[0009] Furthermore, the saturable absorber region has a non-linear saturation absorption characteristic. By changing the bias voltage, the saturation flux and modulation depth of the saturable absorber are regulated, and the absorption degree of the saturable absorber is changed to adjust the pulse width.

[0010] Furthermore, all the interval units are added to the gain region, the gain switch pulse generation mechanism is started, a periodic square wave signal is applied to the gain region, and the period of the square wave signal is adjusted to achieve pulse width adjustment in the range from nanoseconds to hundreds of picoseconds.

[0011] Furthermore, one of the interval units is set as the saturable absorber region. After adjusting the remaining interval units to be the saturable absorber region as well, the Q-switching pulse generation mechanism is started, and the ratio of the length of the saturable absorber region to the length of the gain region is gradually decreased, or the magnitude of the bias voltage is changed to achieve time-domain adjustment from hundreds of picoseconds to picoseconds.

[0012] Furthermore, one of the interval units is set as the saturable absorber region. After adjusting the remaining interval units to be the gain region, the mode-locking pulse generation mechanism is started, and the ratio of the length of the saturable absorber region to the length of the gain region is gradually increased, or the magnitude of the bias voltage is changed to achieve time-domain adjustment from picoseconds to sub-hundred femtoseconds.

[0013] Furthermore, the interval unit farthest from the gain region among the interval units is set as the initial unit of the saturable absorber region, and the remaining interval units are sequentially adjusted to be the saturable absorber region starting from the initial unit to regulate the ratio of the length of the saturable absorber region to the length of the gain region.

[0014] Further, electrical isolation grooves are provided between the interval units, and between the mutual injection coupling region and the gain region. A ridge waveguide is engraved on the surface of the semiconductor laser chip. The gain region is provided with a grating structure. Metal electrode layers for connecting external circuits are respectively plated on the P side and the N side of the semiconductor laser chip. An optical antireflection film is plated on the light-emitting surface of the semiconductor laser chip, and an optical high-reflection film is plated on the opposite end of the light-emitting surface.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects: It solves the problems of single time scale and small pulse width adjustment range of ultra-short pulse lasers. Compared with traditional pulsed lasers, based on the gain-loss mutual injection coupling resonance technology, the present invention provides a mutual injection coupling region including multiple interval units, enabling the length of the saturable absorber region to be dynamically adjustable with the positive and negative changes of the applied bias voltage, and switching the pulse generation mechanism, integrating the mode-locking, Q-switching, and gain-switching schemes on the same semiconductor laser chip. By using multiple pulse width cascade control, it is possible to achieve adjustable pulse widths from sub-100 femtoseconds to nanoseconds on the same chip, greatly broadening the time scale of pulsed lasers. At the same time, compared with existing pulsed semiconductor lasers, the present invention has the characteristics of simple structure, high integration, high electro-optical efficiency, fast response speed, no complex optical path system, and low cost, and has important application values in many fields such as scientific research, industrial processing, biomedicine, and quantum technology. Description of the Drawings

[0016] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings: Figure 1 It is a schematic structural diagram of a semiconductor laser according to an embodiment of the present invention; Figure 2 It is a schematic structural diagram of another semiconductor laser according to an embodiment of the present invention; Figure 3 It is a schematic structural diagram of yet another semiconductor laser according to an embodiment of the present invention; Figure 4 It is a schematic diagram of the semiconductor laser according to an embodiment of the present invention for realizing time domain adjustment.

[0017] Description of the Reference Numerals: a. Mutually-injected coupling region; b. Gain region; 1. First high-reflection film; 2 - 6. First interval units of the first mutually-injected coupling region; 7. First isolation groove; 8. First ridge waveguide; 9. First fixed gain region; 10. First electrode; 11. First antireflection film; 12. DBR; 13 - 17. Second interval units of the second mutually-injected coupling region; 18. Second isolation groove; 19. Second ridge waveguide; 20. Second fixed gain region; 21. Second electrode. Detailed implementation manners

[0018] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not constitute a limitation to the present invention. Similar elements in different embodiments are labeled with related similar element numbers. In the following embodiments, many detailed descriptions are provided to enable a better understanding of the present invention. However, those skilled in the art can easily recognize that some of the features can be omitted in different situations, or can be replaced by other elements, materials, or methods. In some cases, some operations related to the present invention are not shown or described in the specification to avoid submerging the core part of the present invention in excessive descriptions. For those skilled in the art, it is not necessary to describe these related operations in detail, and they can fully understand the related operations based on the descriptions in the specification and general technical knowledge in the art.

[0019] It should be noted that, without conflict, the embodiments and features in the embodiments of the present invention can be combined with each other to form various implementation manners. At the same time, the steps or actions in the method descriptions can also be reordered or adjusted in an obvious manner by those skilled in the art. Therefore, the various sequences in the specification and drawings are only for clearly describing a certain embodiment and do not mean that they are the necessary sequences, unless it is stated that a certain sequence must be followed.

[0020] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by terms such as "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first", "second", etc. may explicitly or implicitly include one or more of such features. In the description of the present invention, unless otherwise specified, the meaning of "a plurality of" is two or more.

[0021] In the description of the present invention, it should be noted that, unless otherwise clearly defined and limited, the terms "mounted", "connected", "coupled" should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or an integral connection; it may be a mechanical connection, an electrical connection; it may be directly connected, or indirectly connected through an intermediate medium, and it may be the communication inside two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood through specific circumstances.

[0022] The time-domain tunable semiconductor laser provided by the present invention can achieve a large range of adjustment of laser pulses on the premise of reducing the structural complexity of the semiconductor laser. Hereinafter, the time-domain tunable semiconductor laser of the present invention and its various parts will be described in detail with reference to the drawings and in conjunction with embodiments.

[0023] Such as Figure 1As shown, for the time-domain tunable semiconductor laser provided by the present invention, an inter-injection coupling region a and a gain region b are provided on the semiconductor laser chip. The inter-injection coupling region a includes multiple section units. By adjusting the absorption / gain characteristics of the section units, the ratio of the length of the saturable absorber region to the length of the gain region in the resonant cavity is controlled, and multiple pulse generation mechanisms are switched to adjust the pulse width. This semiconductor laser can be classified as a gain region or a saturable absorber region by regulating the gain characteristics or absorption characteristics of each section unit accordingly. While controlling the length ratio of the saturable absorber region to the gain region, the pulse generation mechanism is switched to achieve a wide range of pulse width tunability across different time scales. By realizing gain-loss inter-injection coupling resonance in the inter-injection coupling region including multiple section units, the length ratio of the saturable absorber region to the gain region is adjusted. At the same time, multiple pulse generation mechanisms are switched to modulate the pulse width by adjusting the bias voltage or changing the length of the saturable absorber region.

[0024] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, the inter-injection coupling region is made of a material with convertible bias voltage characteristics, and the section units are independently controlled by electrodes. A bias voltage is applied to the section units through the electrodes to adjust the gain / absorption characteristics of the section units. This semiconductor laser can be a monolithic integrated multi-section edge-emitting semiconductor pulse laser, including a multi-section structure of a gain region and an inter-injection coupling region. Electric isolation grooves are etched between each section unit and between the gain region and the inter-injection coupling region to enable independent control of each section unit using independent electrodes. The present invention takes a monolithic semiconductor laser chip as the main body, without introducing an external cavity structure. By controlling the distribution of gain and loss in the resonant cavity and switching the pulse generation mechanism, a wide range of time-domain regulation of the chip-level pulsed semiconductor laser is achieved. This structure has the characteristics of simple structure, high integration, high electro-optical efficiency, fast response speed, no complex optical path system, and low cost, solving the problems of small pulse width adjustment range, complex structure, and large system size of traditional pulsed semiconductor lasers, and improving the stability of time-domain regulation.

[0025] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, when a positive bias voltage is applied to the section unit through the electrode, the section unit is adjusted to have gain characteristics and is added to the gain region. The section unit in the inter-injection coupling region is adjusted to have gain characteristics and is added to the gain region, so that the length of the gain region increases.

[0026] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, correspondingly, when a reverse bias voltage is applied to the interval unit through the electrode, the interval unit is adjusted to have an absorption characteristic, and the interval unit is set as the saturable absorber region. Similarly, the interval unit in the mutual injection coupling region is adjusted to have an absorption characteristic, and this interval unit is added to the saturable absorber region, so that the length of the saturable absorber region increases. The main structure of the present invention is an edge-emitting semiconductor laser chip, including a mutual injection coupling region (2-6) and a gain region (9). The mutual injection coupling region contains several segments of semiconductor materials with convertible characteristics. By changing the bias voltage characteristics, the carrier recombination mechanism can be switched to achieve the dynamic conversion of gain / absorption characteristics. When a forward bias voltage is applied, this region has a gain characteristic. When a reverse bias voltage is applied, this region has an absorption characteristic. At this time, it is equivalent to the SA region, providing nonlinear saturable absorption, absorbing weak light and transmitting strong light, which is the key part for generating pulse signals; the gain region provides sufficient gain for generating laser. Electrical isolation is achieved between each region and each segment structure of the mutual injection coupling region through isolation grooves, ensuring that the voltage or current characteristics on each segment structure do not interfere with each other and can be independently controlled.

[0027] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, the saturable absorber region has a nonlinear saturable absorption characteristic. By changing the magnitude of the bias voltage, the saturation flux and modulation depth of the saturable absorber are regulated, and the absorption degree of the saturable absorber is changed to adjust the pulse width. Due to the nonlinear saturable absorption characteristic of the saturable absorber, starting from the effect of the bias voltage on the carriers, the saturation flux and modulation depth of the absorber are regulated, changing its absorption degree, and realizing an ultra-wide range of pulse width adjustment from nanoseconds to sub-hundred femtoseconds in the conversion of the pulse generation mechanism. In the conversion of the pulse generation mechanism, the ultra-wide range of pulse width adjustment from nanoseconds to sub-hundred femtoseconds can also be achieved by controlling the ratio of gain and loss in the resonant cavity, that is, the ratio of the length of the gain region and the length of the saturable absorber region.

[0028] The following takes the conversion from gain switching to Q-switching and then to mode locking in the conversion of the pulse generation mechanism as an example for illustration.

[0029] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, all interval units are added to the gain region, the gain-switching pulse generation mechanism is activated, a periodic square-wave signal is applied to the gain region, and the period of the square-wave signal is adjusted to achieve pulse-width adjustment in the range from nanoseconds to picoseconds. In this way, all the interval units in the mutual injection coupling region are adjusted to have gain characteristics, so they are all added to the gain region, and the gain-switching pulse generation mechanism is activated. Here, activating the gain-switching pulse generation mechanism is not the result of all interval units being added to the gain region, but two consecutive actions. On these two premises, a periodic square-wave signal is applied to the gain region, and the pulse-width adjustment in the range from nanoseconds to picoseconds can be achieved by adjusting the period of the square-wave signal. A periodic square-wave signal can be applied to the gain region through an external drive circuit. The intensity of the optical signal changes with the fluctuation of the electrical signal, and the pulse width of the laser is approximately the same as the duration of the high level. By adjusting the period of the square-wave signal, the pulse-width control in the range from nanoseconds to picoseconds can be achieved.

[0030] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, one interval unit is set as the saturable absorber region. After adjusting the remaining interval units to be the saturable absorber region as well, the Q-switching pulse generation mechanism is activated, and the ratio of the length of the saturable absorber region to the length of the gain region is gradually reduced, or the magnitude of the reverse bias voltage applied to the saturable absorber region and the magnitude of the forward bias voltage applied to the gain region are changed to achieve time-domain adjustment from picoseconds to femtoseconds. Here, one interval unit is always set as the saturable absorber region, and the purpose of this setting is to facilitate the subsequent activation of the Q-switching pulse generation mechanism and the mode-locking pulse generation mechanism. For example, when the Q-switching pulse generation mechanism is activated and the remaining interval units are adjusted to be the saturable absorber region, the Q-switching pulse generation mechanism can adjust the pulse by gradually reducing the ratio of the length of the saturable absorber region to the length of the gain region, or by changing the magnitude of the reverse bias voltage applied to the interval unit.

[0031] When the pulse generation mechanism of the semiconductor laser is the Q-switching pulse generation mechanism, the semiconductor laser chip is divided into two sections: the saturable absorber region and the gain region. As Figure 2As shown in the figure, the interval unit 2 is set as a fixed saturable absorber region, and the first fixed gain region 9 is a fixed gain region. The interval units 3-6 can either be combined with the interval unit 2 as a saturable absorber region or be combined with the first fixed gain region 9 as a gain region. The lengths of the saturable absorber region and the gain region determine the pulse width of the semiconductor laser output. The principle is as follows: when the saturable absorber region exhibits non-linear saturable absorption characteristics under reverse bias, all the photons generated by the gain region are absorbed by the absorber and cannot lasing. As the photon density gradually increases, the high energy levels of the saturable absorber region are all occupied and cannot absorb more photons, and the saturable absorber region becomes transparent, and the semiconductor laser can lase. The transparent state of the saturable absorber region can only be maintained for a very short time, and the saturable absorber will return to the absorption state again. The pulse width of the semiconductor laser depends on the recovery time of the saturable absorber. When controlling the loss injection into the gain, that is, the proportion of the saturable absorber region decreases and the length of the gain region increases, the saturation energy of the saturable absorber decreases, the recovery time also decreases, and the pulse width shortens accordingly. At the same time, by adjusting the reverse bias voltage of the saturable absorber region, the recovery time of the saturable absorber can be changed to obtain a more precise time-domain regulation, and the pulse width regulation from picoseconds to picoseconds can be realized.

[0032] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, after setting one interval unit as a saturable absorber region and adjusting the remaining interval units as gain regions, the mode-locked pulse generation mechanism is started, and the ratio of the length of the saturable absorber region to the length of the gain region is gradually increased, or the magnitude of the bias voltage is changed to achieve time-domain adjustment from picoseconds to sub-100 femtoseconds. Combining Figure 2 As shown in the figure, any interval unit in the mutual injection coupling region can be set as a saturable absorber region, and then the remaining interval units are adjusted as gain regions. The semiconductor laser provided by the present invention can switch different pulse generation mechanisms of the semiconductor laser by regulating the gain characteristics and absorption characteristics of the interval units in the mutual injection coupling region, and can generate laser pulses with adjustable pulse widths from sub-100 femtoseconds to dozens of picoseconds. By regulating the gain characteristics of the interval units in the saturable absorption region and the mutual injection coupling region, the pulse width adjustable from sub-100 picoseconds to nanoseconds can be realized.

[0033] The pulse generation mechanism of the semiconductor laser is the mode-locking mechanism. When the control loss is injected into the gain, making the loss small enough and the gain large enough, the length of the saturable absorber region is minimized, the loss is greatly reduced, and the gain saturation effect in the gain region appears. The saturable absorber region saturates before the gain region and recovers before the gain region, forming a shorter transparent window than the Q-switching pulse generation mechanism. The multi-longitudinal modes with disordered phases in the resonator are superimposed on each other to form an optical signal with randomly fluctuating intensity. When passing through the gain region, the strong and weak signals experience the same gain; when passing through the saturable absorber region, the weak light is absorbed, while the strong light can pass through. Therefore, the weak light gradually disappears and the strong light continuously strengthens, ultimately forming a pulse signal with phase-locked multi-longitudinal modes. By adjusting the reverse bias voltage of the saturable absorber region, the recovery time of the saturable absorber can be changed, realizing the regulation of the pulse width in the range from picoseconds to sub-100 femtoseconds.

[0034] In summary, the semiconductor laser provided by the present invention combines three pulse generation mechanisms: gain switching, Q-switching, and mode-locking. By regulating the gain and loss in different regions, or regulating the saturation flux and recovery time of the saturable absorber, the gain and loss are mutually injected and coupled in resonance, achieving an ultra-wide time-domain tuning range from nanoseconds to sub-100 femtoseconds.

[0035] The time-domain tunable semiconductor laser provided by the present invention adopts a multi-section structure design, including a gain region and a mutual injection coupling region. The saturable absorber region includes different interval units, which are independently controlled by different electrodes. Among them, the interval units in the mutual injection coupling region can be converted into a gain region or a saturable absorption region by applying a bias voltage through an electrode. When a forward bias voltage is applied to the interval unit, electrons transition from the excited state to the ground state, electron-hole recombination occurs, and photons are released, showing gain characteristics, and this interval unit is classified as the gain region. When a reverse bias voltage is applied to this interval unit, electron-hole pairs are pulled by the reverse electric field, absorb photons and cannot recombine, showing absorption characteristics, and this interval unit is classified as the saturable absorber region. Within a certain range, the longer the length of the saturable absorber region, the higher the modulation depth, and the stronger the non-linear modulation effect of the absorber, which makes the pulse width of the output laser of the semiconductor laser narrower. When the length ratio of the saturable absorber region exceeds a certain range, due to excessive loss introduced, the compensation speed of the gain is lower than the dynamic response of the loss, and the phase locking of the multi-longitudinal modes cannot be maintained continuously. The semiconductor laser tends to enter the periodic gain release mode, that is, Q-switching mode-locking. When the length ratio of the saturable absorber region further increases, the loss dominates the laser generation process, and the laser enters the full Q-switching mode. In addition, this semiconductor laser can also achieve nanosecond-level optical pulses through the gain switching mechanism.

[0036] As a preferred embodiment, in the time-domain tunable semiconductor laser provided by the present invention, the interval unit farthest from the gain region in the interval unit is set as the initial unit of the saturable absorber region, and the remaining interval units are sequentially adjusted to the saturable absorber region starting from the initial unit, so as to adjust the ratio of the length of the saturable absorber region to the length of the gain region. This embodiment combines Figure 2 As shown, the interval unit 2 farthest from the first fixed gain region 9 in the interval unit is set as the initial unit of the saturable absorber region. Therefore, adjusting the remaining interval units to the saturable absorber region means sequentially adjusting the remaining interval units to the saturable absorber region starting from the initial unit end, so as to adjust the ratio of the length of the saturable absorber region to the length of the gain region.

[0037] The first fixed gain region 9 here is always the gain region. The interval units in the mutual injection coupling region can be set as the gain region or the saturable absorber region. The interval unit farthest from the gain region in the interval units of the mutual injection coupling region is set as the saturable absorber region and is set as the initial unit of the saturable absorber region. The meaning of the initial unit here is that on the premise of temporarily maintaining the absorption characteristics of the initial unit, starting from the initial unit 2, the remaining interval units are sequentially adjusted to the saturable absorber region. For example, the interval unit 3 is adjusted to the saturable absorber region, and the interval units 4-6 are adjusted to the gain region. At this time, the ratio of the length of the saturable absorber region to the length of the gain region is: the length of interval unit 2 + the length of interval unit 3 / the length of interval unit 4 + the length of interval unit 5 + the length of interval unit 6 + the length of the first fixed gain region 9. Next, the interval unit 4 is adjusted to the saturable absorber region, and the interval units 5-6 are adjusted to the gain region. At this time, the ratio of the length of the saturable absorber region to the length of the gain region is: the length of interval unit 2 + the length of interval unit 3 + the length of interval unit 4 / the length of interval unit 5 + the length of interval unit 6 + the length of the first fixed gain region 9. And so on, the pulse width is adjusted by adjusting the ratio of the length of the saturable absorber region to the length of the gain region.

[0038] As a preferred embodiment, electrical isolation grooves are provided between the interval units, as well as between the mutual injection coupling region and the gain region. A ridge waveguide is etched on the surface of the semiconductor laser chip. The gain region is provided with a grating structure. Metal electrode layers for connecting external circuits are respectively plated on the P side and the N side of the semiconductor laser chip. An optical antireflection film is plated on the light-emitting surface of the semiconductor laser chip, and an optical high-reflection film is plated on the opposite end of the light-emitting surface. The ridge waveguide etched on the chip surface is used to confine the optical field, and the gain region with a grating structure is used for spectral compression and to reduce pulse broadening caused by dispersion. Metal electrode layers are respectively plated on the P side and the N side of the chip for connecting external circuits to apply bias voltages to each interval unit. An optical antireflection film is plated on the light-emitting end face of the chip, and a high-reflection film is plated on the other end for enhancing the light output power. In the preparation process flow, first, methods such as plasma-enhanced chemical vapor deposition, photolithography, and plasma etching are used to fabricate gratings, ridge waveguides, electrode windows, and isolation grooves on the chip surface. After completing the preparation of the physical structure of the semiconductor laser chip, metal electrode layers are grown on the P side and the N side respectively. Finally, an antireflection film is plated on the light-emitting cavity surface of the chip, and a high-reflection film is plated on the opposite cavity surface.

[0039] Compared with the prior art, the present invention can achieve the following beneficial effects: It solves the problems of single time scale of ultra-short pulse lasers and small pulse width adjustment range. Compared with traditional pulse lasers, the present invention switches the pulse generation mechanism, integrates three schemes of mode locking, Q-switching, and gain switching on the same semiconductor laser chip, and sets a mutual injection coupling region including multiple interval units based on the gain-loss mutual injection coupling resonance technology, enabling the length of the saturable absorber region to be dynamically adjustable with the positive and negative changes of the applied bias voltage. Multiple pulse width cascade control can be realized, and pulse widths adjustable from sub-100 femtoseconds to nanoseconds can be achieved on the same chip, greatly broadening the time scale of pulsed lasers. At the same time, compared with existing pulsed semiconductor lasers, the present invention has the characteristics of simple structure, high integration, high electro-optical efficiency, fast response speed, no complex optical path system, and low cost, and has important application values in many fields such as scientific research, industrial processing, biomedicine, and quantum technology.

[0040] Embodiment 1 The present embodiment provides a semiconductor pulse laser with ultra-wide time-domain tunability, as Figure 2 shown. The multi-segment laser chip can be divided into a mutual injection coupling region and a gain region. The first mutual injection coupling region includes interval units 2 to 6 and the first fixed gain region 9. The specific structure further includes a first isolation groove 7 for realizing electrical isolation, a first ridge waveguide 8 for confining the optical field, a first electrode 10 for connecting an external circuit, a first high-reflection film 1 for increasing the light output power, and a first antireflection film 11.

[0041] The total cavity length of the semiconductor laser is 4.5 mm, the total length of the mutual injection coupling region is 850 μm, the length of each segment of the first interval units 2 - 6 is 170 μm, and the length of the first fixed gain region 9 is 3400 μm; the width of the first isolation groove is 50 μm; the width of the first ridge waveguide is 5 μm; the grating period of the first fixed gain region is 75.9 μm, the reflectivity of the first high - reflection film is 99%, and the reflectivity of the first anti - reflection film is 3%.

[0042] A forward bias voltage is applied to the first interval units 2 - 6 and the first fixed gain region 9 of the mutual injection coupling region, and an external drive circuit is connected to apply a periodic square - wave signal to the gain region. At this time, all regions on the semiconductor laser chip are gain regions, and the pulse generation mechanism of the semiconductor laser is the gain - switching pulse generation mechanism. By adjusting the period of the square - wave signal, pulse - width control in the range from nanoseconds to picoseconds can be achieved.

[0043] Among them, the characteristics of the first high - reflection film 1 are: high reflectivity, enhanced resonance, and increased output optical power. For the interval units 2 - 6 of the mutual injection coupling region: each segment is controlled by an independent electrode, and a forward / reverse bias voltage is applied to make it have gain / absorption characteristics. When a forward bias voltage is applied, this region acts as a gain region; when a reverse bias voltage is applied, it acts as a saturable absorber region, providing nonlinear saturable absorption, absorbing weak light and transmitting strong light. The saturable absorber region needs to start from 2 and be continuous; the gain region needs to start from 6 and be continuous. When the length of the saturable absorber region decreases, the saturation energy of the saturable absorber decreases and the recovery time is shortened, accelerating the pulse - generation process and obtaining pulses with a narrower time scale; when the length of the gain region decreases and the length of the saturable absorber region increases, the saturation energy of the saturable absorber increases and the recovery time is extended, delaying the pulse - generation process and obtaining wider pulses. The first isolation groove 7: realizes electrical isolation of each segment structure between interval units, as well as between the mutual injection coupling region and the gain region, ensuring that the voltages applied to each segment structure do not interfere with each other and can be independently controlled. The first ridge waveguide 8: limits the transverse optical - field distribution. The first fixed gain region 9: provides gain. A grating structure is set in the first fixed gain region for spectral compression, suppressing pulse broadening and distortion. The first electrode 10: connects to the external drive circuit. The first anti - reflection film 11: has high transmittance and increases output optical power.

[0044] For the mutually-injected saturable absorber region, the mechanism for the semiconductor laser to generate pulses is the Q-switching pulse generation mechanism, and the pulse width of the semiconductor laser depends on the recovery time. Subsequently, the loss is injected into the gain to reduce the loss and increase the gain. By sequentially changing the interval units 6, 5, 4, and 3 to forward bias voltages, the proportion of the length of the saturable absorber region gradually decreases while the proportion of the length of the gain region gradually increases. That is, the saturation energy of the saturable absorber decreases, the recovery time also decreases, and the pulse width shortens accordingly. After changing the voltage polarity of the bias voltage, adjusting the magnitude of the reverse bias voltage can change the recovery time of the saturable absorber, obtain a more refined time-domain regulation, and achieve pulse width regulation from picoseconds to femtoseconds.

[0045] When the absorption decreases to the point where the gain saturation effect appears, the mechanism for the semiconductor laser to generate pulses is the mode-locking pulse generation mechanism. By controlling the magnitude of the bias voltage to change the recovery time of the absorber, pulse width regulation in the range from picoseconds to sub-femtoseconds can be achieved.

[0046] Example 2 Based on Example 1, by changing parameters such as the total length of the semiconductor laser chip, the length of the mutual injection coupling region, the length of the gain region, the width of the isolation groove, and the grating period, the regulation of the pulse width can refer to Example 1.

[0047] Example 3 Based on Example 1, the number of segments of the interval units in the mutual injection coupling region can be arbitrarily divided according to actual needs, and the lengths of each segment of the interval units can be the same or different.

[0048] Example 4 Based on Example 1, replace the grating structure of the gain region with any structure having mode selection or filtering functions, such as a gain grating, a refractive index grating, or a surface grating.

[0049] Example 5 As Figure 3As shown in the figure, on the basis of Embodiment 1, the grating structures of the first high-reflection film and the gain region are removed, and a Distributed Bragg Reflector (DBR) 12 is introduced for dispersion management and to increase the reflectivity of the cavity surface, reducing the influence of dispersion on pulse broadening and replacing the Distributed Feedback (DFB) structure. Second isolation groove 18: realizes electrical isolation between each interval unit, as well as between the second mutual injection coupling region and the second fixed gain region 20, ensuring that the voltages applied to each section of the structure do not interfere with each other and are independently controlled. Second ridge waveguide 19: restricts the transverse optical field distribution. Second fixed gain region 20: provides gain. A grating structure is arranged in the second fixed gain region for spectral compression, suppressing pulse broadening and distortion. Second electrode 21: connects to an external drive circuit.

[0050] The second interval units 13 - 17 of the mutual injection coupling region: each section is controlled by an independent electrode, and a forward / reverse bias voltage is applied to it to make it have gain / absorption characteristics. When a forward bias voltage is applied, this interval unit acts as a gain region; when a reverse bias voltage is applied to this interval unit, it acts as a saturable absorber region, providing non-linear saturable absorption, absorbing weak light, and transmitting strong light. The saturable absorber region needs to start from interval unit 2. Interval unit 2 can be used as the initial unit of the saturable absorber region first, and then interval units 3 - 6 are set in sequence and kept continuous; the gain region needs to start from interval unit 6, and 5, 4, 3, 2 are set in sequence and kept continuous. When the length of the saturable absorber region decreases, the saturation energy of the saturable absorber decreases and the recovery time is shortened, accelerating the pulse generation process and obtaining pulses with a narrower time scale; when the length of the gain region decreases and the length of the saturable absorber region increases, the saturation energy of the saturable absorber increases and the recovery time is extended, delaying the pulse generation process and obtaining wider pulses.

[0051] The multi-section time-domain tunable semiconductor laser chip provided in this embodiment adjusts the pulse width based on the above principle, achieving a pulse width adjustment from 289 ps to 5.3 ns, as Figure 4 shown.

[0052] The object of this patent is to solve the problems of single time scale and small adjustment range of ultra-short pulse lasers. Compared with traditional pulsed lasers, this invention integrates multiple ultra-short pulse technologies. Based on gain-loss mutual injection coupling resonance, multiple mutual injection coupling regions are set, enabling the length of the saturable absorber to be dynamically adjustable with the positive and negative changes of the applied voltage, thus changing the pulse generation mechanism. The mode-locking, Q-switching, and gain-switching schemes are integrated on a single semiconductor laser chip, thereby changing the time scale of pulse generation. By using multiple pulse width cascade control, it is possible to achieve adjustable pulse widths from sub-100 femtoseconds to nanoseconds on a single chip, greatly broadening the time scale of pulsed lasers. At the same time, compared with existing pulsed semiconductor laser schemes, this structure has the characteristics of simple structure, high integration, high electro-optical efficiency, fast response speed, no complex optical path system, and low cost, and has important application value in many fields such as scientific research, industrial processing, biomedicine, and quantum technology.

[0053] The above specific implementation manners do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations, and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A time-domain tunable semiconductor laser, characterized in that: A mutual injection coupling region and a gain region are set on a semiconductor laser chip. The mutual injection coupling region includes a plurality of interval units. The ratio of the length of the saturable absorber region and the length of the gain region in the resonant cavity is controlled by adjusting the absorption / gain characteristics of the interval units, and a plurality of pulse generation mechanisms are switched to adjust the pulse width.

2. The semiconductor laser according to claim 1, characterized in that: The mutual injection coupling region is made of a material with convertible bias voltage characteristics, and the interval units are independently controlled by electrodes. The gain / absorption characteristics of the interval units are adjusted by applying a bias voltage to the interval units through the electrodes.

3. The semiconductor laser according to claim 2, characterized in that: When a forward bias voltage is applied to the interval unit through the electrode, the interval unit is adjusted to have a gain characteristic, and the interval unit is increased to the gain region.

4. The semiconductor laser according to claim 2, characterized in that: When a reverse bias voltage is applied to the interval unit through the electrode, the interval unit is adjusted to have absorption characteristics, and the interval unit is set as a saturable absorber region.

5. The semiconductor laser according to claim 4, characterized in that: The saturable absorber region has nonlinear saturation absorption characteristics. The saturation flux and modulation depth of the saturable absorber are regulated by changing the bias voltage, thereby changing the absorption degree of the saturable absorber and adjusting the pulse width.

6. The semiconductor laser according to claim 5, characterized in that: All of the interval units are added to the gain zone, a gain switch pulse generation mechanism is started, a periodic square wave signal is applied to the gain zone, and the period of the square wave signal is adjusted to achieve pulse width regulation in the range of nanoseconds to hundreds of picoseconds.

7. The semiconductor laser according to claim 5, characterized in that: One of the interval units is set as the saturable absorber region, and after the remaining interval units are adjusted to be the saturable absorber region, a Q-switched pulse generation mechanism is started to gradually reduce the ratio of the length of the saturable absorber region to the length of the gain region, or the magnitude of the bias voltage is changed to achieve time domain adjustment from hundreds of picoseconds to picoseconds.

8. The semiconductor laser according to claim 5, characterized in that: One of the interval units is set as the saturable absorber region, and after adjusting the remaining interval units to the gain region, a mode-locked pulse generation mechanism is started, and the ratio of the length of the saturable absorber region to the length of the gain region is regulated to gradually increase, or the magnitude of the bias voltage is changed to achieve time domain regulation from picoseconds to sub-hundred femtoseconds.

9. The semiconductor laser according to claim 8, characterized in that: The one of the interval units farthest from the gain region is set as an initial unit of the saturable absorber region, and the remaining interval units are sequentially adjusted from the initial unit to be the saturable absorber region to adjust the ratio of the length of the saturable absorber region to the length of the gain region.

10. The semiconductor laser according to claim 1, characterized in that: An electrical isolation groove is arranged between the interval units and between the mutual injection coupling region and the gain region. A ridge waveguide is engraved on the surface of the semiconductor laser chip. A grating structure is arranged in the gain region. The P surface and N surface of the semiconductor laser chip are respectively plated with metal electrode layers for connecting to an external circuit. The light emitting surface of the semiconductor laser chip is plated with an optical anti-reflection film, and the opposite end of the light emitting surface is plated with an optical high-reflection film.

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