39 results about "Quantum dot lasers" patented technology

A multilayer quantum dot laser growth method based on a stress compensation technology comprises the following steps: S1, removing an oxide layer from an N-type substrate, and respectively growing an N-type GaAs buffer layer, an N-type AlvGa1-vAs limiting layer and a GaAs waveguide layer I; s2, growing an In < w > Ga < 1-w > As quantum well, an InAs quantum dot, an In < x > Ga < 1-x > As cover layer, a GaAs cover layer, a GaAs spacing layer I and the like on the GaAs waveguide layer I; s3, circulating S2 for a set number of times so as to realize the growth of the multi-layer quantum dot material; and S4, respectively growing a GaAs waveguide layer II, a P-type Al < z > Ga < 1-z > As limiting layer and a P-type GaAs metal contact layer on the GaAs spacing layer II. According to the invention, the GaAsP material with a small lattice constant is utilized, and the stress caused by the InGaAs material is reduced, so that the uniformity and quality of the multi-layer quantum dot laser structure are improved.

The application discloses a kind of high-power high-speed direct modulation quantum dot laser and preparation method thereof, N-type GaAs substrate is sent into MBE chamber to remove the surface oxidation layer, N-type GaAs contact layer is sequentially grown on the N-type GaAs substrate of surface oxidation layer removal, N-type AlGaAs restriction layer, first undoped GaAs waveguide layer, multilayer quantum dot active region, second undoped GaAs waveguide layer, P-type AlGaAs restriction layer, P-type GaAs contact layer, to obtain high-power high-speed direct modulation quantum dot laser from this. The method greatly improves the number of quantum dot layers by precisely controlling the growth conditions of quantum dots and the thickness of the spacer layer, while controlling the thickness of the quantum dot active region, thereby increasing the differential gain of quantum dots, carrier injection efficiency and greatly improving the direct modulation rate and light output power of quantum dot laser.

The invention provides a quantum dot DFB laser based on a substrate buried grating. The quantum dot DFB laser comprises a substrate; the buffer layer is formed on the substrate; the N-type doped lower coating layer is formed on the buffer layer; the quantum dot active region is formed on the N-type doped lower coating layer; the P-type doped upper coating layer is formed in the quantum dot active region; and the N-type doped lower coating layer comprises a buried grating structure layer. The invention further provides a preparation method of the quantum dot DFB laser based on the substrate buried grating, and the flow ratio and the growth rate of the five-family elements and the three-family elements are optimized when the grating layer grows and the grating layer is buried. Through the design that the grating is buried on the lower substrate, the problem of damage of high temperature to a quantum dot active region in a traditional process is reduced, meanwhile, the limiting layer epitaxial design is optimized, the vertical divergence angle of a light field is reduced, the optical fiber coupling loss is reduced, and multi-mode oscillation is reduced.

The invention provides an on-chip light source based on a quantum dot laser mutual injection system, which comprises a chip substrate, a master quantum dot laser and a slave quantum dot laser, and is characterized in that a waveguide is arranged between the master quantum dot laser and the slave quantum dot laser; the main quantum dot laser and the slave quantum dot laser are completely identical in structure and are respectively provided with a buffer layer and an active layer, the buffer layer of the main quantum dot laser and the buffer layer of the slave quantum dot laser are fixedly arranged on the chip substrate, and the waveguide is arranged between the active layer of the main quantum dot laser and the active layer of the slave quantum dot laser. The beneficial effects of the invention are that the relative intensity noise (RIN) and spectral line width of output laser can be significantly reduced, and the output laser power is greatly improved.

The present invention discloses a quantum dot laser with a low threshold and a preparation method thereof, which includes a quartz substrate, a silica periodic grating, a quantum dot layer, and a silica protective layer stacked in sequence. The quantum dot layer is composed of closely packed mercury selenide quantum dots with a diameter of 4.8 nm to 6.6 nm, mercury sulfide quantum dots with a diameter of 4 nm to 5.2 nm, quantum dots with a core / alloy / shell structure of mercury selenide / mercury cadmium selenide / cadmium selenide with an effective exciton diameter of 4.8 nm to 6.4 nm, or quantum dots with a core / alloy / shell structure of mercury sulfide / mercury cadmium sulfide / cadmium sulfide with an effective exciton diameter of 4 nm to 5 nm. The present invention realizes environmentally stable electron doping in quantum dots by controlling the size of the quantum dots, uses the doped quantum dots as the gain medium of the laser, and further realizes a low gain threshold, a low laser threshold, sustainable continuous laser output, and a designable output wavelength.

The present invention relates to a photonic circuit for generating squeezed light, comprising: an electron-pumping source (SPS) that pumps electrons at a constant rate, a distributed optical-feedback quantum dot laser component (QDL), the laser component being electrically coupled to the silent pump and integrated into a semiconductor substrate, the laser component having a predefined threshold current. The silent pump is configured to inject, into the laser component, a supply current with an intensity proportional to the intensity of the predefined threshold current by a factor between 1 and 5, so as to make the laser component generate a phase-squeezed or amplitude-squeezed light beam.

The invention provides an optical frequency comb modulation system for a quantum dot mode-locked laser, which comprises a quantum dot mode-locked laser, a light splitting element, an optical feedback path and an optical measurement path, and is characterized in that the quantum dot laser is internally provided with a laser cavity, and two ends of the quantum dot laser can output laser; one end of the quantum dot laser is connected with the input end of the light splitting element, the output end of the light splitting element is connected with the input end of the optical feedback path and the input end of the optical measurement path, and a first deviation controller and a back reflector which are matched with each other are arranged in the optical feedback path. The quantum dot laser, the light splitting element, the first deviation controller and the back reflector are connected through optical fibers or waveguides. The method has the advantages that tuning of the modulation state of the optical frequency comb can be achieved, the distribution range of the FM comb is compressed, and the working range of the AM comb is widened.

The invention discloses an electric pumping colloidal quantum dot laser of a silicon-based substrate, and belongs to the technical field of semiconductor optoelectronic devices. The laser is provided with a doped silicon substrate, a lower buffer layer, a lower carrier transport layer, a colloidal quantum dot gain layer, an upper carrier transport layer, an upper protection layer, a waveguide structure layer, an upper buffer layer and an electrode system which are stacked from bottom to top. A conductive optical limiting structure is constructed on the surface of the doped silicon substrate and has conductivity in the vertical direction, and the effective refractive index of the conductive optical limiting structure under the lasing wavelength is remarkably lower than that of the colloid quantum dot gain layer. In addition, a DFB grating structure is arranged in the transparent waveguide structure layer, and a planarization buried layer design is adopted to adapt to a solution method preparation process. The problems of silicon-based interface light leakage, parasitic waveguide effect and process compatibility are solved, and low-cost, low-threshold and high-stability laser output can be realized on the silicon substrate without wafer bonding.

A quantum dot laser-based self-injection locking frequency stabilization system provided by the present invention comprises a quantum dot laser, a light splitting element and a reflection unit, the quantum dot laser is internally provided with a laser cavity, the two ends of the quantum dot laser can output laser, and the light splitting element and the reflection unit are sequentially arranged along the laser emission direction of one end of the quantum dot laser. The quantum dot laser, the light splitting element and the reflection unit are connected through optical fibers or waveguides, and a part of laser beams output from one end of the quantum dot laser can be separated by the light splitting element and reflected back into the laser cavity through the reflection unit to be output from the other end of the quantum dot laser. The quantum dot laser has the beneficial effects that the output frequency stability and high-precision control of the quantum dot laser are improved, the structure is simple, the cost is low, the radio frequency spectrum line width of the quantum dot laser is optimized, and the time jitter performance of the pulse of the quantum dot laser is improved.

The invention provides a method for reducing relative intensity noise of a quantum dot laser and a quantum communication light source, and belongs to the technical field of quantum dot lasers. The method is realized by reducing external carrier noise of a pumping source, so that the silicon-based quantum dot laser generates light in an amplitude compression state, the relative intensity noise of the quantum dot laser is reduced, and the light source prepared by the method for reducing the relative intensity noise of the quantum dot laser can be used as a quantum communication light source. The silicon-based laser has the beneficial effects that the performance of the silicon-based laser is greatly optimized, and the output stability and reliability of the silicon-based laser are improved.

The present application discloses an InAs quantum dot laser and a preparation method thereof. The InAs quantum dot laser includes a GaAs substrate, a lower cladding layer, a plurality of InAs quantum dot active regions, and an upper cladding layer stacked in sequence; each InAs quantum dot active region includes a first InGaAs quantum well layer, a quantum dot layer, a second InGaAs quantum well layer, and a GaAs spacer layer stacked in sequence; wherein, there is no doping source in the quantum dot layer, and the average thickness of the GaAs spacer layer of each InAs quantum dot active region is 10 - 50 nm. In the present application, there is no doping source in the quantum dot layer. By reasonably controlling the average thickness of each GaAs spacer layer, the uniformity of the quantum dots is gradually improved, the linewidth enhancement factor is reduced, and the antireflection performance of the laser is stronger. Among them, the antireflection performance can be increased to at least above -10 dB, so that the isolator in the optical module can be removed to solve the technical problems of large volume, high cost, and low integration degree caused by the optical module with an isolator.

The application discloses a method for preparing a quantum dot laser light source by coupling of periodically arranged optical materials. By modulating the resonance coupling between a photonic crystal microcavity and a quantum dot light-emitting wavelength, a continuous spectrum laser light source is realized. The preparation method of the photonic crystal microcavity is as follows: a PDMS stamp with a special periodic arrangement shape is prepared in advance, HPC material is spin-coated on the light-emitting electrode side of a bottom-emitting quantum dot device, the prepared PDMS stamp is used to press a periodic arrangement pattern, then optical material is spin-coated and deposited on the pattern, and the HPC material is washed away with a solvent after spin-coating, so that a photonic crystal microcavity with a certain periodic air hole is obtained. The modulation of the optical properties of the photonic crystal microcavity can be realized by adjusting the PDMS stamp template. The method can construct a photonic crystal microcavity with a specific energy band structure on the light-emitting side of the bottom-emitting quantum dot device, so that a high-brightness and high-quality laser light source is obtained.

The invention discloses an InAs quantum dot laser and an InAs quantum dot laser preparation method, and belongs to the technical field of semiconductor lasers. The energy band and the waveguide of the epitaxial structure are jointly designed, the epitaxial structure adopts the multi-layer stacked lower gradient waveguide layer and the multi-layer stacked upper gradient waveguide layer, and the refractive indexes of the gradient waveguide layers are distributed in a gradient manner, so that continuous and convergent deflection can be performed on light rays in the gradient waveguide layers, and the light rays can be continuously deflected in the gradient waveguide layers. Light emitted from the end face of the gradient waveguide layer has a velocity component closer to the normal direction, so that the divergence angle of a light beam is reduced; and meanwhile, the epitaxial structure adopts the multi-layer stacked InAs quantum dot active region, so that the density of the quantum dots is multiplied, and the energy band of the InAs quantum dot active region is optimized, thereby increasing the optical gain volume and reducing the threshold current density. And only the epitaxial structure is designed, and the method can be compatible with the existing process, so that the process complexity and cost are reduced.

The invention provides a quantum dot laser, and a quantum dot laser bandwidth and nonlinear performance coordinated regulation and control method, device and equipment. The method comprises the following steps: constructing the quantum dot laser into a nonlinear resonant subsystem driven by bias current; applying a bias current to the quantum dot laser; the quantum dot laser is set at a cooperative bias working point by regulating and controlling the magnitude of the bias current, and the cooperative bias working point is configured to cooperatively improve the relaxation oscillation frequency of the laser and control the nonlinear effect.

The present invention relates to a photonic circuit for generating compressed light, comprising: a constant-rate electron pumping (SPS) source, a distributed optical feedback quantum dot (QDL) laser component, the laser component being electrically coupled to the silent pump and integrated into a semiconductor substrate, the laser component having a predefined threshold current. The silent pump is configured to inject, into the laser component, a supply current with an intensity proportional to the intensity of the predefined threshold current by a factor between 1 and 5, so as to cause the laser component to generate a beam of light compressed in phase or amplitude. Figure for the abstract: Figure 1

The application discloses a kind of electrically pumped colloidal quantum dot lasers of silicon-based substrate, belong to the technical field of semiconductor optoelectronic devices.The laser is stacked from bottom to top with doped silicon substrate, lower buffer layer, download carrier transport layer, colloidal quantum dot gain layer, upper carrier transport layer, upper protective layer, waveguide structure layer, upper buffer layer and electrode system.Doped silicon substrate surface is constructed with conductive optical confinement structure, the structure has vertical direction conductivity, and its effective refractive index at lasing wavelength is significantly lower than colloidal quantum dot gain layer.In addition, DFB grating structure is provided in transparent waveguide structure layer, and flat buried layer design is used to adapt solution method preparation process.The application solves the problems of silicon-based interface light leakage, parasitic waveguide effect and process compatibility, and can realize low-cost, low-threshold and high-stability laser output on silicon substrate without wafer bonding.

The present invention discloses a quantum dot laser-based photon microwave signal generator and acquisition method. The generator includes a tunable semiconductor laser, a quantum dot laser, an aspheric lens, a beam splitter, a neutral density plate, a fiber Bragg grating, an isolator, a beam splitter, and a photodetector. The output light of the tunable semiconductor laser is injected into the quantum dot laser. The single-cycle oscillation light output by the quantum dot laser is focused by the aspheric lens and then split into two parts by the beam splitter. One part of the light is filtered by the fiber Bragg grating and fed back into the cavity of the quantum dot laser. The other part of the light is focused by the isolator and the aspheric lens in turn and then split into two parts by the beam splitter. One part is the output photon microwave signal, and the other part is converted into an electrical signal by the photodetector for microwave signal quality detection and adjustment. The present invention solves the problems of wide linewidth and high phase noise of light-injected semiconductor lasers, significantly improving the quality of photon microwaves.

Hybrid silicon quantum dot laser (HSQDL) structure including an optical waveguide of a first width, a mesa of a second width and a current channel of a third width that is smaller than the second width. In some examples, the third width is only slightly larger than the first width to narrowly confine electrical current directly over the optical waveguide while the third width is significantly larger than the first width to efficiently transport heat away from the optical gain medium. While the current channel has a low electrical resistivity, other regions of the mesa contributing to the third width have a higher electrical resistivity. In some examples, an implant process is practiced to increase electrical resistivity.

The invention specifically discloses a surface high-power high-speed directly-modulated quantum dot laser and a preparation method thereof, an N-type GaAs substrate is sent into an MBE cavity to remove an oxide layer on the surface, and an N-type GaAs contact layer, an N-type AlGaAs limiting layer, a first undoped GaAs waveguide layer, a multi-layer quantum dot active region, a second undoped GaAs waveguide layer and a P-type AlGaAs limiting layer are sequentially grown on the N-type GaAs substrate with the oxide layer on the surface removed. And a P-type GaAs contact layer is formed, so that the surface high-power high-speed directly-modulated quantum dot laser is obtained. According to the method, the number of layers of the quantum dots is greatly increased by accurately controlling the growth conditions of the quantum dots and the thickness of the spacer layer, and the thickness of the active area of the quantum dots is controlled at the same time, so that the differential gain and the carrier injection efficiency of the quantum dots are increased, and the direct modulation rate and the light output power of the quantum dot laser are greatly improved.

The invention relates to the technical field of warehouse management, and discloses an intelligent component warehouse management system and method based on digital twinning, and the system comprises a stress management unit, a conduction management unit, a change management unit, a compensation management unit and a twinning management unit. Time domain-frequency domain cross characteristics of temperature and humidity data and vibration data can be accurately captured, the non-linear interaction of multiple physical fields and a lattice distortion management graph generated by a conduction management unit are prevented from being omitted, the distortion risk of a quantum dot active area can be recognized in advance, a phonon energy management spectrum of each quantum dot generated by a change management unit, and the quantum dot active area distortion risk can be recognized in advance. According to the quantum dot laser, the dynamic change of lattice distortion can be tracked, the spectral shape compensation signal, generated by the compensation management unit, of the reverse direction of each quantum dot can be offset, the central wavelength drift and the twin management instruction generated by the twin management unit can be offset, management lag can be avoided, the damage probability of the quantum dot laser is reduced, and the warehouse management reliability is improved.

The invention relates to the technical field of laser devices, in particular to a flexible colloidal quantum dot laser device and a preparation method thereof. The device structure sequentially comprises a first reflecting layer, a first optical isolation layer, a second reflecting layer, a second optical isolation layer, a gain dielectric layer, a third optical isolation layer, a third reflecting layer, a fourth optical isolation layer and a fourth reflecting layer from bottom to top. The four reflecting layers are respectively right, left, left and right hand reflecting layers or left, right, right and left hand reflecting layers; the left / right chiral reflecting layer is a polymer cholesteric liquid crystal film; the gain dielectric layer is made of colloidal quantum dots; materials of the first to fourth optical isolation layers are respectively selected from polymethyl methacrylate, polystyrene and the like. The method has the advantages that different chiral cholesteric liquid crystal stacks are used to construct a high-quality F-P resonant cavity; the light emitted by the gain medium achieves a total reflection effect, thereby effectively enhancing the optical feedback and reducing the ASE threshold. A full-solution treatment process is adopted, preparation is easy and convenient, and cost is low.

The invention discloses a low-threshold quantum dot laser and a preparation method thereof. The low-threshold quantum dot laser comprises a quartz substrate, a silicon dioxide periodic grating, a quantum dot layer and a silicon dioxide protective layer which are sequentially stacked. The quantum dot layer is composed of densely stacked mercury selenide quantum dots with the diameter of 4.8 nm to 6.6 nm, mercury sulfide quantum dots with the diameter of 4 nm to 5.2 nm, and mercury selenide / mercury cadmium selenide / cadmium selenide core / alloy / shell structure quantum dots with the effective exciton diameter of 4.8 nm to 6.4 nm or mercury sulfide / mercury cadmium sulfide / cadmium sulfide core / alloy / shell structure quantum dots with the effective exciton diameter of 4 nm to 5 nm. According to the invention, environment-stable electron doping in the quantum dots is realized by controlling the size of the quantum dots, and the doped quantum dots are used as a gain medium of the laser, so that low gain threshold, low laser threshold, sustainable continuous laser output and designable output wavelength are realized.

Hybrid silicon quantum dot laser (HSQDL) structure including an optical waveguide of a first width, a mesa of a second width and a current channel of a third width that is smaller than the second width. In some examples, the third width is only slightly larger than the first width to narrowly confine electrical current directly over the optical waveguide while the third width is significantly larger than the first width to efficiently transport heat away from the optical gain medium. While the current channel has a low electrical resistivity, other regions of the mesa contributing to the third width have a higher electrical resistivity. In some examples, an implant process is practiced to increase electrical resistivity.

The application discloses a preparation method of a near-infrared vertical cavity surface laser with low threshold and high gain based on weakly confined quantum dots, and belongs to the technical field of quantum dot lasers. A CdS shell layer is grown on the weakly confined double-tapered CdSe quantum dots, and the thickness of the CdS shell layer is controlled to be 2 layers by controlling the injection amount of dodecanethiol; the CdSe / CdS quantum dots are spin-coated on the high-reflection surface of two Bragg reflectors (DBRs); and the surfaces coated with the quantum dots are close to each other and are spliced to form a vertical cavity surface laser. The vertical cavity surface laser constructed by taking the weakly confined double-tapered hexahedral CdSe / CdS quantum dots as deep red gain material has deep red / near-infrared laser emission of 720 nm, an extremely low laser threshold of 11.23 µJ / cm 2 and an extremely wide gain bandwidth of 670-730 nm.

The present application provides a method for fabricating an active feedback laser and an active feedback laser. The method includes: sequentially growing a buffer layer and an active region structure on a deoxidized substrate to obtain a laser growth structure; dividing the laser growth structure into a DFB region and an IFB region, and performing bandgap blue shift on the quantum dot active region in the IFB region through regional annealing to obtain a first-stage laser structure, then sequentially performing ridge waveguide etching and coplanar N-type electrode region etching, and performing sidewall grating etching on the ridge waveguide corresponding to the DFB region; and performing electrical isolation etching at the adjacent position of the DFB region and the IFB region to obtain an active feedback laser. By integrating a quantum dot DFB laser and a quantum dot IFB region with bandgap blue shift, the problem that it is difficult to meet its application in low-cost high-speed direct modulation due to the low modulation bandwidth of the quantum dot gain medium laser is solved, and the low-cost requirement of high-speed direct modulation quantum dot lasers is achieved.

The invention relates to the technical field of laser gain material synthesis, in particular to a low-threshold quantum dot laser gain film and a preparation method thereof. Comprising the following steps: in an inert gas atmosphere, preparing a zinc oleate precursor solution, a cadmium oleate precursor solution, a tri-n-octylphosphine-selenium precursor solution and a tri-n-octylphosphine-sulfur precursor solution; preparing a mixed solution on site, including a mixed solution A, a mixed solution B and a mixed solution C; preparing the core-shell quantum dots by adopting a step-by-step thermal injection method, namely preparing a core, a continuous gradient layer and a protective layer; purifying the core-shell quantum dots by using a purifying agent, and performing post-treatment to form a dispersion liquid; and spin-coating the dispersion liquid to a substrate by adopting a one-step spin-coating method, and annealing to form the low-threshold quantum dot laser gain film. The quantum dot core-shell material has the advantages that the prepared quantum dot core-shell material has a gradient energy level gradient structure, the quantum dots can obtain a smooth constraint potential barrier from the core to the shell through the gradient structure, non-radiative recombination of the quantum dots is improved, and the laser performance of the material is improved, namely the ASE threshold value of the quantum dots is reduced.

The invention discloses a high-power liquid quantum dot laser amplifier, which is characterized in that a pump light beam is divided into a light path I and a light path II after entering the laser amplifier, and the light path I and the light path II simultaneously reach a second liquid quantum dot laser medium after being separated; the light path I is sequentially provided with a beam splitter, a cylindrical mirror, a first liquid quantum dot laser medium, a reflective blazed grating, a tunable total reflective mirror, an output coupling mirror, a total reflective mirror, a diaphragm, a collimating lens and a second liquid quantum dot laser medium along the incident direction of a pumping light beam; the light path II is sequentially provided with a beam splitter, two right-angle prisms arranged in a mirror image mode, a collimating lens, a focusing lens and a second liquid quantum dot laser medium in the incident direction of the pump light beam. The method provided by the invention is stable and universal, stable, high-power and tunable liquid quantum dot laser output is realized, and the defects that a gain medium of an organic dye molecule laser in the prior art is easy to inactivate and the working stability is low under high power are effectively overcome.

The invention provides a method for compressing the spectral line width of a laser, a local oscillator and a coherent detection system, and belongs to the technical field of coherent light communication. The method for compressing the spectral line width of the silicon-based quantum dot laser is realized by reducing the external carrier noise of the pumping source, so that the frequency noise of the silicon-based quantum dot laser is reduced, and the phase fluctuation of output light is reduced; and the method for compressing the spectral line width of the silicon-based quantum dot laser can be used for preparing a coherent detection local oscillator light source. The silicon-based quantum dot laser has the beneficial effects that the line width of the silicon-based quantum dot laser is remarkably reduced, the re-broadening phenomenon is inhibited, the performance of the silicon-based laser is greatly optimized, and the output stability and reliability of the silicon-based quantum dot laser are improved.

A method for growing a multilayer quantum dot laser based on stress compensation technology, comprising: S1, removing an oxide layer from an N-type substrate, and performing N-type GaAs buffer layer, N-type Al v Ga 1‑v As confinement layer and GaAs waveguide layer 1 are grown; S2, In w Ga 1‑w As quantum wells, InAs quantum dots, In x Ga 1‑x As cap layer, GaAs cap layer, GaAs spacer layer 1, etc. are grown; S3, S2 is cycled for a set number of times to achieve the growth of multi-layer quantum dot materials; S4, GaAs waveguide layer 2, P-type Al z Ga 1‑z As limiting layer and P-type GaAs metal contact layer are grown. The present invention utilizes GaAsP material with a smaller lattice constant to reduce the stress brought by InGaAs material, so as to improve the uniformity and quality of the multi-layer quantum dot laser structure.

The application provides a quantum dot laser-based true random number generation method, comprising the following steps: simulating a chaotic laser signal generated by a quantum dot laser; setting a sampling step h to extract light intensity data of the chaotic laser signal, smoothing the signal by using a Savitzky-Golay filter to obtain an original light intensity data sequence; performing differential derivation on the original light intensity data sequence to generate a preliminary extreme value output sequence; performing symmetric quantization on the extreme value output sequence in a maximum value descending order sorting and a minimum value ascending order sorting manner to generate a preliminary binary quantization sequence; enhancing randomness of the preliminary binary quantization sequence; performing NIST randomness testing on a final high-quality random number sequence to output a high-quality true random number sequence meeting a testing quality requirement. The application has the beneficial effects that the true random number generator can realize the combination of high speed, high stability, small size and optical applicability.