101 results about "Laser threshold" patented technology

A method for stripping large-area GaN-based epitaxial layer by low-power laser features that the pulse laser beam is used to scan the GaN-loased epitaxial film grown on the sapphire substrate from outside to inside while the sapphire substrate is heated and the laser threshold is biased.

The invention relates to a random-distribution feedback optical fiber laser which can realize stable, space-irrelevant and continuous laser output, and belongs to the technical field of the optical fiber laser. The random-distribution feedback optical fiber laser comprises a pump laser, a wavelength division multiplexer, a fiber bragg grating, an Er-doped optical fiber, an optical fiber Raman laser and a long monomode optical fiber. The reflection effect of the fiber bragg grating is combined with the distributed Rayleigh scattering effect of the optical fiber to form a distributed random feedback optical resonant cavity; and the light is subjected to gain amplification by an Er-doped optical fiber and the stimulated Raman scattering effect. Compared with the random-distribution feedback optical fiber laser reported before, the threshold value of the pump laser and the length of the monomode optical fiber can be reduced, and the limitation on stimulated emission wavelength and the wavelength number by a Rayleigh gain peak is broken through, thereby realizing the purpose of tuning the laser wavelength. The random-distribution feedback optical fiber laser is suitable for fields, such as remote optical fiber sensing, remote communication and the like.

A method for stabilizing an output of a pulsed laser system includes a directly modulated laser diode by mitigating the effect of switching transients on the temporal shape of the outputted pulses. The method includes controlling a pulse shaping signal to define, over time, processing and conditioning periods. During the processing periods, the pulse shaping signal has an amplitude profile tailored to produce the desired temporal shape of the output. Each conditioning period either immediately precedes or follows a processing period. During a given processing period, the amplitude profile of the pulse shaping signal is tailored so that the drive current of the laser diode is lower than its maximum value during the corresponding processing period, and is of the same order of magnitude as the laser threshold current of the laser diode. In this manner, the stability of the output during the corresponding processing period is improved.

The invention discloses 3.7-4.2-micron all-solid-state laser orientated intermediate infrared holmium-neodymium dual-doped laser crystal, and relates to the field of an intermediate infrared laser gain material. In the laser crystal, trivalent holmium ions are used as active ions, and the corresponding energy level transition is Ho3<+>: 5I5-5I6; the trivalent neodymium ions have dual functions, which can be used as the trivalent holmium ion sensitized ions to enable the crystal to be suitable for commercial and high-power LED pumping on one hand; on the other hand, the trivalent holmium ions also can be used as de-activation ions of the trivalent holmium ions to greatly shorten the energy level service life of the lower laser energy level 5I6 of the trivalent holmium ions; meanwhile, the energy level service life of the upper laser energy level 5I5 of the trivalent holmium ions is not changed obviously, so that population inversion can be realized, effective laser output is achieved, and the laser threshold value can be lowered and laser efficiency can be improved; and the laser crystal can be used for 3.7-4.2-micron laser output and has the significant application prospects in the fields of medical treatment, scientific research, military affairs and the like.

Seed pulse generators for fiber amplifier systems include a seed pump controller coupled to a seed pump laser diode. A photodetector is situated to detect seed pulse generation, and is coupled to the seed pump controller so that seed pumping is decreased upon pulse detection. For a laser diode pump source, a pump current can be pulsed to produce a seed pulse and then decreased to a bias level such as a DC bias current that is less than a pump laser threshold current. Single seed pulses can be generated with reduced pulse jitter.

To reduce the laser threshold by efficiently exciting a light-emitting body in a solid-state dye laser with light having high density, thereby facilitating emission of laser beams, and to miniaturize a solid-state dye laser including an excitation light source. A solid-state dye laser capable of emitting laser beams by efficiently introducing light from an excitation light source to a light-emitting body incorporated in an optical resonator structure and exciting the light-emitting body with light with high density, is realized.

A method is provided for determining a laser threshold of a laser diode, which is operated by a drive circuit as a function of a first signal in a first feedback and a second signal in a second feedback, the first feedback being supplied via an optical coupling of an optical output signal of the laser diode. The method is characterized in that the second feedback is supplied by an electrical signal picked up between the drive circuit and the laser diode, the electrical signal is compared with an adjustable activation threshold, only a portion of the electrical signal that exceeds the adjustable activation threshold is transmitted to the drive circuit in such a way that the second feedback is active only when such a portion occurs, the adjustable activation threshold is changed in such a way that the activity state of the second feedback changes, and the laser threshold of the laser diode is determined as a function of the value of the adjustable activation threshold during a change in the activity state of the second feedback. Furthermore, a drive circuit is presented which carries out the method.

This invention discloses a Q-modulated semiconductor laser with an electric absorption structure including a distributed feed-back grating of lambda / 4 phase shift, two separated upper electrodes depositing on the top of the grating, an electrode depositing on the base of the laser as the public base, in which, the first upper electrode covers part of the grating including a phase shift region providing gain to the laser by injecting constant current, a second upper electrode covers the rest part of the grating away from the phase shift region as the Q-modulator of the laser and electric signals can be added to the second upper electrode to change the absorption coefficient of the waveguide of the modulator region and alter the Q value of the laser so as to alter the laser threshold value and output power.

The invention relates to an indenofluorene-based conjugated polymer laser gain material, a method for preparing the same and application of the indenofluorene-based conjugated polymer laser gain material. Indenofluorene structures are used as frameworks for the indenofluorene-based conjugated polymer laser gain material, different receptor structures are selected, copolymerization is carried out to obtain trapezoidal block copolymers, a general structural formula of the trapezoidal block copolymers is shown, an R in the general formula I represents one of alkyl, alkoxy, alkyl phenyl and alkoxy phenyl of C1-C30, and an A represents electron receptor structure modification units. The indenofluorene-based conjugated polymer laser gain material, the method and the application have the advantages that the indenofluorene-based conjugated polymer laser gain material is low in cost, high in yield and good in solubility, and synthesis is simple and controllable; the indenofluorene-based conjugated polymer laser gain material is good in heat stability, reversible in oxidation-reduction characteristic and excellent in film-forming properties, and film devices can be prepared by the aid of simple solution film-forming modes; the indenofluorene-based conjugated polymer laser gain material is high in brightness and excellent in luminescence efficiency when used as an active luminescence layer in organic electroluminescent devices, is low in laser threshold and high in gain when applied to organic laser devices and is a luminescent material system with important application prospect.

The invention discloses a fused silica element zero probability damage threshold prediction method based on photo-thermal weak absorption; the method comprises the following steps: pre-processing the surface areas of a standard fused silica element sample of the same model with a to-be-tested fused silica element in different levels; carrying out photo-thermal detection on the areas processed in different levels so as to obtain a photo-thermal detection value, and carrying out a laser threshold test so as to obtain a zero probability damage threshold; building a photo thermal detection-zero probability damage threshold association curve model of the to-be-tested fused silica element according to the photo-thermal detection values and corresponding zero probability damage thresholds of all areas; carrying out photo-thermal detection for the to-be-tested fused silica element so as to obtain the photo-thermal detection value, searching the corresponding zero probability damage threshold according to the photo thermal detection-zero probability damage threshold association curve model, thus obtaining the zero probability damage threshold of the to-be-tested fused silica element. The method can realize nondestructive test on the fused silica element, is simple in operation, high in accuracy, high in sensitivity, and can satisfy laser optical system usage requirements.

A high-power frequency doubling single-frequency laser generating device for phase modulation and demodulation comprises a single-frequency laser (1), a first phase modulator (2), an optical fiber amplifier (4), a spatial isolator (5), a frequency doubling device (6) and a second phase modulator (7) which are connected in sequence, and further comprises a signal generator (3). The device is characterized in that the signal generator (3) generates two periodic signals with the same shape and frequency, the first phase modulator (2) and the second phase modulator (7) are driven respectively, thephase difference of the two periodic signals is npi-delta phi, wherein n is an odd number, delta phi is phase delay generated by laser transmission amplification between the second phase modulator (7) and the first phase modulator (2), and the modulation depth of the second phase modulator (7) is twice that of the first phase modulator (2). Single-frequency fundamental frequency light is generated through single-frequency fundamental frequency light phase modulation, a laser SBS threshold value is improved, high-power multi-single-frequency frequency doubling light is obtained after amplification and frequency doubling, the frequency doubling light is subjected to phase demodulation, and high-power single-frequency frequency doubling light is obtained. According to the scheme, the single-frequency laser has the characteristic of frequency doubling line width before phase modulation, has the characteristics of simple and flexible structure, good light beam quality and the like, provides a new scheme for frequency doubling of the high-power single-frequency laser, and has an important practical value.

The invention discloses a 4-8[mu]m-pulse Raman all-fiber laser, and belongs to the field of the laser. The 4-8[mu]m-pulse Raman all-fiber laser comprises a light source, a gain fiber I and a gain fiber II that are connected in sequence, wherein a first resonant cavity and a second resonant cavity are formed in the gain fiber I; a multi-order stokes optical resonant cavity is formed in the gain fiber II; the first resonant cavity and the second resonant cavity are partially overlapped; and a pulse switch is arranged in a place, which is not overlapped with the first resonant cavity, in the second resonant cavity. According to the 4-8[mu]m-pulse Raman all-fiber laser provided by the invention, the 4[mu]m intermediate infrared Q-switched pulse and Raman Q-switched pulse laser with wavelength of greater than 4[mu]m can be efficiently realized under the normal temperature, so that the laser threshold value can be greatly lowered, the output efficiency can be improved, and the cost loss is relatively low; and in addition, the Raman all-fiber laser has the characteristics of easy integration, facilitated practical application, and capability of realizing 3.9[mu]m laser efficient output under a non-cooling room temperature condition.

The invention relates to a wide-tuning ultrafast laser crystal material and application thereof. The wide-tuning ultrafast laser crystal material is characterized in that the laser crystal material consists of ytterbium ion doped bismuth silicate laser crystals (Yb: Bi12SiO20, Yb: BSO for short). Yb ions have large energy level splitting in the BSO laser crystals so that the material has a low laser threshold and a large tuning width in laser application. The growth of the Yb: BSO crystals can be obtained by adopting various crystal growth methods such as a pulling method, a Bridgman method, a zone melting method and the like. The excellent laser optical characteristics of the Yb: BSO crystals realize a laser diode (LD) direct pumped low-threshold wide-tuning ultrafast laser, so that lasers are simpler and more miniature.

The invention discloses a random fiber laser based on stimulated Raman effect and belongs to the technical field of fiber lasers. The random fiber laser comprises a first fiber Bragg grating, a first random phase shifting fiber Bragg grating, a Raman pumping laser source, a wavelength division multiplexer, a single mode fiber, a second random phase shifting fiber Bragg grating and a second fiber Bragg grating. The common fiber Bragg gratings are used for reflecting pumping light, the random phase shifting fiber Bragg gratings provide random light feedback, and laser threshold power can be effectively lowered. The stimulated Raman effect is used for achieving light gain, Random pumping light wavelength and fiber Bragg grating center lengths can be changed, and random laser output with different wavelengths is obtained. The laser has the advantages of being simple in structure, easy to manufacture, low in threshold power and the like.

The invention provides a high-power slab green laser. The high-power slab green laser includes a pump source, a focusing system, a laser resonator and a self-frequency doubling crystal. The self-frequency doubling crystal is a neodymium ion doped calcium borate rare earth salt crystal cut into a slab shape along a direction of a maximum non-principal effective nonlinear coefficient of the crystal.Phase matching of different wavelengths is realized by changing a tangential direction of the crystal so as to realize laser output in 545 nm or 550 nm band. The pump source is a laser diode array having an emission center wavelength of 808 nm or 880 nm. An input cavity mirror and an output cavity mirror are coated with suitable film systems so as to obtain high-power laser output in the 545 nm or 550 nm band. The laser of the invention has the advantages of low laser threshold, high conversion efficiency and output power, and simple laser structure.

The invention belongs to the technical field of physical laser and relates to a tunable ultrashort pulse laser device with an eye-safe wave band; two endoscopes are respectively arranged on the same plane; a laser crystal, a group-velocity mismatch compensation device, a diaphragm and a phase mismatch compensation device are respectively arranged at intervals on the connecting line between the centers of the two endoscopes; a non-linear crystal and a trichroic endoscope are respectively arranged in inclination at the lower side of the centre line of the endoscopes arranged in an inclination structure; a diode laser device and a cooling device are arranged on the side of the laser crystal; the diode laser device is controlled by a driving power supply system; the laser crystal is pumped bythe diode laser device to combine the non-linear crystal and the trichroic endoscope; the tunable ultrashort pulse laser generated by mode-locked laser oscillation is realized by using the positive and negative directions of a light wave through the cascading second-order nonlinear effect of the non-linear crystal. The tunable ultrashort pulse laser device with the eye-safe wave band has the advantages of simple structure, small volume, low cost, low laser threshold value, low laser ion concentration and good prospect of application.

The invention relates to an amplification output method and system for an optical signal. The amplification output method comprises the following steps that: when laser driving current matched with arequired output optical signal and laser threshold value current are in a first relationship, a direct current signal is emitted to drive a laser, the laser emits pump light by first output power, thepump light is coupled to a gain optical fiber, and the gain optical fiber amplifies the output optical signal; and when the laser driving current matched with the required output optical signal and the laser threshold value current are in a second relationship, the duty cycle of the high current and the low current of a PWM (Pulse-Width Modulation) signal is set, the PWM signal is emitted to drive the laser, the laser emits pump light by second output power, the pump light is coupled to the gain optical fiber, and the gain optical fiber amplifies the output optical signal. No matter whether the target power required by the laser is large or small, the optical signal can be kept stable, and a gain effect is guaranteed.

The invention discloses a preparation method of a photonic crystal optical fiber preform. The preparation method comprises the following main steps: firstly dissolving ytterbium trichloride hexahydrate and aluminum trichloride hexahydrate in an alcohol water solution, further adding a sufficient amount of high-purity silicon dioxide powder into the solution, stirring to obtain a suspension, then stirring the suspension for not less than 20min, then drying, further putting dry ion-doped quartz powder into a high-oxygen and high-temperature environment for dehydration, and finally melting in the high-oxygen environment to obtain the optical fiber preform. Compared with a traditional process, the preparation method disclosed by the invention has the advantages of uniform doping, high doping concentration, no electrode pollution and the like, and the prepared photonic crystal optical fiber preform has good physical properties and optical properties of high purity, nearly no hydroxy groups, high heat loss threshold, good heat stability, higher laser threshold and the like.

The invention discloses an organic solid laser based on a gold-silver core-shell nanorod-metal film. The organic solid laser comprises a substrate, a metal film layer, a gold-silver core-shell nanorodstructure layer and a gain dielectric layer which are sequentially stacked, wherein the metal film layer is a metal film capable of generating a non-local surface plasma effect SPP; a shell layer material in the gold-silver core-shell nanorod structure layer is Ag, and a central core material is Au nanorods. According to the invention, the gold-silver core-shell nanorods are deposited on the metal film layer at a proper distance to form a composite structure of the gold-silver core-shell nanorods and the metal film layer; and random laser is enhanced by utilizing a strong local field and a scattering effect generated by coupling of the LSPR of the gold-silver core-shell nanorod and the SPP of the metal film in the composite structure, so that the laser threshold of the organic solid laseris remarkably reduced.

The invention relates to a bis-indenofluorene conjugated polymer laser gain material and a preparing method and application thereof. The material is a trapezoidal block copolymer obtainerd by adopting a trapezoidal bis-indenofluorene structure as a skeleton and choosing and copolymerizing different receptor structures, and the structural formula of the material is shown in the following general formula I, wherein R1, R2 is one of alkyl, alkoxy, alkylbezene and alkoxyphenyl of C1-C30, and A is an electronic receptor structure modification unit. The material has the advantages of being low in cost, easy and controllable to synthesize, high in yield, good in solubility and the like; meanwhile, the material has good thermal stability, a reversible redox property and good film forming performance, can be prepared into a thin film device by adopting a simple solution film forming mode, present high brightness and excellent light-emitting efficiency in an organic electroluminescent device as an active light-emitting layer, present a low laser threshold value and high gain in an organic laser device at the same time, and is a light-emitting material system with an important application potential.

The invention relates to a method and a device for enhancing the stability of an extinction ratio of an optical module. According to the method, a relation curve that a laser threshold current is changed along with temperature is firstly fit, and then an initial relation curve that the modulation current needed for stabilizing the output of the extinction ratio is changed along with the temperature is acquired via conversion. When the external environment changes, the modulation current of the optical module laser is adjusted according to the change relation of the initial curve through monitoring the temperature, the extinction ratio of an optical signal transmitted by the optical module can be adjusted in real time, and thus the stabilization of the extinction ratio of the optical moduleis achieved. When the extinction ratio of the optical signal output by the optical module under the high temperature or low temperature state deviates from a stable value set by the initial relationcurve due to the reason that the chips or devices have consistency deviation, the modulation current actually needed at such a point can be inversely computed through monitoring the actual value of the extinction ratio of the output optical signal, and thus the correction curve of the modulation current that is changed along with the temperature in the whole temperature range is fed back and fit,and the stabilization of the extinction ratio of the optical signal is enhanced.

The invention discloses a laser threshold current testing method and also discloses a laser threshold current testing device. According to the laser threshold current testing method and the laser threshold current testing device provided by the invention, through a method of setting threshold comparison, a threshold current testing error problem caused by testing environment noise interference, laser device nonlinearity and testing equipment performance in a laser threshold current testing is solved, the correct laser threshold current can be determined, thus the testing efficiency and the good product rate are greatly improved, the requirements of the testing environment and testing equipment are reduced, and the method and the device have a very high practical value.

The invention discloses an Er-Ho-Pr tri-doped lead fluoride mid-infrared laser crystal and a preparation method thereof. According to the invention, in a growing Er-Ho-Pr tri-doped lead fluoride crystal, as Er ions can be excited under 980nm LD, the transition of Er ions from <4>I11 / 2 to <4>I13 / 2 can generate fluorescence near 2.7 micrometers, at the same time a part of energy is transferred fromthe <4>I11 / 2 energy level of Er ions to the <5>I6 energy level of Ho ions, so that transition of Ho ions from <5>I6 to <5>I7 can generate fluorescence near 2.9 micrometers, therefore the full width athalf-maximum of a mid-infrared spectrum can reach 330nm; the incorporation of Pr ions not only enhances the energy transfer efficiency between the <4>I11 / 2 energy level of Er ions and the <5>I6 energy level of Ho ions, but also greatly reduces the <4>I13 / 2 energy level lifetime of Er ions and the <5>I7 energy level lifetime of Ho ions, is conducive to realizing population inversion and laser output, reduces the laser threshold and improves laser efficiency.

A hybrid distributed amplification method based on a random fiber laser generated within erbium fiber with low doping concentration, i.e. weak erbium-doped fiber (WEDF), which includes: Step 1. constructing a fiber link via WEDF; Step 2. generating the random fiber laser based on the fiber link, the pump source, the wavelength division multiplexer and the strong feedback module; Step 3. constructing the spatial equalized gain based on hybrid gain of the erbium fiber and random fiber laser; Step 4. the signal is amplified by the hybrid spatial equalized gain. The present invention solves the typical problem of high laser threshold and low pump conversion efficiency when conventional fiber is used to generate random fiber laser for distributed amplification.

The invention discloses a method and device for measuring intracavity loss of a solid laser, and the method comprises the steps: firstly drawing an input-output power curve of the laser according to the injection pumping power of the laser and the corresponding laser output power, and then calculating the intracavity loss of the solid laser through the measured laser threshold value of the laser and the obtained input-output power curve. Reading a group of laser output power corresponding to the injection pumping power at a position higher than a laser threshold value, calculating to obtain the oblique efficiency of the laser, and then calculating to obtain the size of a resonant cavity mode waist spot at a laser crystal by utilizing an ABCD matrix at the injection pumping power; and finally, the oblique efficiency of the laser and the square value of the ratio of the resonant cavity mode waist spot at the laser crystal to the pumping laser waist spot are obtained through calculation, so that the intra-cavity loss value of the laser is obtained through quick and accurate calculation, and the method can be used for measuring the intra-cavity loss of the fundamental frequency light solid-state laser with single transverse mode, single longitudinal mode and multi-mode output.