Dielectric metasurfaces is a plane optical device to achieve the desired function by modulating amplitude and phase, polarization for the incident light, and its transmission efficiency is higher than other metasurfaces, these advantages lead to dielectric metasurfaces will be used widely in the future. Nevertheless, the majority of metasurfaces are planar singlelayered structure, which limit seriously the view field and effect of monochromatic imaging. Here, we demonstrate a composed dielectric meta-lens doublet by the electromagnetic simulation can achieve perfectly diffraction-limited monochromatic focus for the polarization-insensitive incident lights at a wavelength of 375 nm, which has the view field of 60°, the numerical aperture of 0.5, and a focal length of 380μm. Due to the dielectric meta-lens doublet has the scaling of subwavelength at ultraviolet light, and the devices have high distinguishability, it can be used widely in nanolithography, imaging with large view field, and other optical domains.
During 2014-2016, the Laser guide star (LGS) adaptive optics (AO) system observation campaign has been carried out on Lijiang 1.8 meter telescope. During the campaign, two generation LGS AO systems have been developed and installed. In 2014, a long-pulsed solid Sodium prototype laser with 20W@400Hz, a beam transfer optical (BTO) system, and a laser launch telescope (LLT) with 300mm diameter were mounted onto the telescope and moved with telescope azimuth journal. At the same time, a 37-elements compact LGS AO system had been mounted on the Bent-Cassegrain focus and got its first light on observing HIP43963 (mV= 8.18mv) and reached Sr=0.27 in J Band after LGS AO compensation. In 2016, the solid Sodium laser has been upgrade to stable 32W@800Hz while D2a plus D2b repumping is used to increase the photon return, and a totally new LGS AO system with 164-elements Deformable Mirror, Linux Real Time Controller, inner closed loop Tip/tilt mirror, Multiple-PMT tracking detector is established and installed on the telescope. And the throughput for the BTO/LLT is improved nearly 20%. The campaign process, the performance of the two LGS AO systems especially the latter one, the characteristics of the BTO/LLT system and the result are present in this paper.
The AO progresses for astronomy in the Key Laboratory of Adaptive Optics, Chinese Academy of Sciences are reported in this presentation. For night-time astronomical observations, the recent AO technological developments, such as Laser Guide Star, Pyramid Sensor and Deformable Secondary Mirror, are introduced. The solar AO researches are also presented for day-time astronomical observations. Furthermore, we will show the on-sky high resolution observational results in the 1.8m telescope at Gaomeigu site, Yunnan Observatory and the 1-m New Vacuum Solar Telescope (NVST) at Fuxian Lake Solar Observatory respectively.
KEYWORDS: Accelerated life testing, Semiconductor lasers, High power lasers, Data modeling, Failure analysis, Lithium, Continuous wave operation, Analytical research, Defense and security, Optoelectronic devices
High power semiconductor laser is widely used because of its high transformation efficiency, good working stability, compact volume and simple driving requirements. Laser’s lifetime is very long, but tests at high levels of stress can speed up the failure process and shorten the times to failure significantly. So accelerated life test is used here for forecasting the lifetime of 808nm CW GaAs/AlGaAs high power semiconductor laser that has an output power of 1W under 1.04A. Accelerated life test of constant current stress based on the Inverse Power Law Relationship was designed. Tests were conducted under 1.3A, 1.6A and 1.9A at room temperature. It is the first time that this method is used in the domestic research of laser’s lifetime prediction. Applying Weibull Distribution to describe the lifetime distribution and analyzing the data of times to failure, characteristics lifetime’s functional relationship model with current is achieved. Then the characteristics lifetime under normal current is extrapolated, which is 9473h. Besides, to confirm the validity of the functional relationship model, we conduct an additional accelerated life test under 1.75A. Based on this experimental data we calculated the characteristics lifetime corresponding to 1.75A that is 171h, while the extrapolated characteristics lifetime from the former functional relationship model is 162h. The two results shows 5% deviation that is very low and acceptable, which indicates that the test design is reasonable and authentic.
A composite tracking sensor, in which a reflect mirror with a central hole is inserted in the imaging systems so that the reflective beam beyond the hole is directed to the large dynamic range detector and the beam passing the hole is reimaged by a lens to enter the high sensitivity detector, can be used for tip-tilt detecting with high accuracy and large dynamic range simultaneously. A composite tracking sensor prototype based on the multi-anode photo-multiplier tubes (MAPMT) is developed for 1.8 meter astronomical telescope in the Gaomeigu astronomical observation station. In this paper, the principle of the composite tracking sensor is introduced. The prototype is described in detailed and the experimental results are presented. The results show that this composite tracking sensor can reach the tracking accuracy of 0.2 μrad and higher within the dynamic range of 870 μrad.
Based on the demands of high sensitivity, precision and frame rate of tip/tilt tracking sensors in acquisition, tracking and pointing (ATP) systems for satellite-ground optical communications, this paper proposes to employ the multiple-anode photo-multiplier tubes (MAPMTs) in tip/tilt tracking sensors. Meanwhile, an array-type photon-counting system was designed to meet the requirements of the tip/tilt tracking sensors. The experiment results show that the tip/tilt tracking sensors based on MAPMTs can achieve photon sensitivity and high frame rate as well as low noise.
Adaptive control of a tip-tilt mirror requires precise model estimation, which is difficult for the nonlinear features of
piezoelectric actuators such as creep, hysteresis and resonance. A linear quadratic Gaussian control/loop transfer
recovery (LQG/LTR) based compensation of the non-linearity is used, which employs a high sampling frequency
position sensor to measure the displacements of the tip-tilt mirror and feedbacks the modified command needed to make
the actuator response linearly to input command. A normalized LMS adaptive filter whose gains are adjusted by weight
updating algorithm to minimize the mean square error of the output is used in order to reduce the jitter introduced by
kinds of broadband and narrowband disturbance. The principle of an adaptive filter and LQG/LTR compensator
combination control of a nonlinear tip-tilt mirror is introduced. The method is compared with the integrator and
LQG/LTR combination control by numerical simulation. Results reveal that the adaptive filter and LQG/LTR
compensator combination control is more effective and has less tracking residual error.
A simple cw mode-locked solid-state laser, which is end-pumped by a low-power laser diode, was demonstrated by optimizing the laser-mode size inside the gain medium. The optimum ratio between mode and pump spot sizes inside the laser crystal was estimated for a cw mode-locked laser, taking into account the input pump power. Calculation and experiment have shown that the optimum ratio was about 3 when the pump power is 2 W, which is different from the value regularly used in passively mode-locked solid-state lasers. This conclusion is also helpful in increasing the efficiency of high-power ultrashort lasers.
Design of the typical laser diode side-pumped Nd:YAG rod system has been discussed using the conventional ray tracing method in this paper. Firstly introduce two basic matrices, refractional and translational matrix, described the transmission of nonparaxial light ray in the medium without concerning the absorption of light. And then, using those matrices, analyze the distribution of pump light in the crystal respectively under the condition of directly pumped system and indirectly pumped system with a cylindrical quartz rod as focusing lens. From the result of simulation, we compare the advantage and disadvantage of the two pumped method, and mainly consider how to select the diameter of the focus lens and cooling tube, indicate the effect of deionized water and cooling tube have on the pump light distribution in the active material. At last, make some conclusions about the side-pumped Nd:YAG laser system.
We report on optoelectronic multiple chip modules, consisting of vertical cavity surface emitting laser (VCSEL), photodetector and 1.2 micrometer CMOS electronic circuit. The hybrid integrated components operate at a date rate of 155 Mb/s, which could be used in optical interconnects for multiple computers.
Novel multi-active region semiconductor lasers with large coupled optical cavity and high quantum efficiency, and new mechanism tunneling-regenerated multi-active region light emitting diodes with high quantum efficiency and high brightness have been proposed and fabricated. The external and differential quantum efficiency are 2.9 and 3.0 W/A, and the output light power as high as approximately 5 W when the injecting current equals 2A for the four active region 980 nm strained InGaAs/GaAs QW lasers. The fundamental mode light output with perpendicular angle <EQ 17 degrees for this type of large coupled optical cavity laser has been achieved. The on-axis luminous intensity of the new mechanism 620 nm AlGaInP/AlInP LEDs with two active regions is more than 5 cd. It was theoretically and experimentally resulted in that the electro-luminescence efficiency and the on-axis luminous intensity are linearly increasing approximately with the number of the active regions.
980 nm InGaAs/InGaAsP/AlGaAs strained quantum well lasers with novel large optical cavity and asymmetrical claddings was fabricated by MOCVD. Very high differential quantum efficiency of 90% (1.15 W/A) and low vertical divergence angle of 24 degree(s) at long cavity length were obtained for 100 micrometers stripe lasers. The differential quantum efficiency is up to 94% (1.20) at cavity length of 500 micrometers .
Native Oxide AlAs layer were employed to block the current injection from the top anode. The luminous intensity exceeded 75 mcd of the LED chip with native oxide. AlAs layer sandwiched 5 micrometer AlGaAs current spreading layer under 20 mA current injection. Electrical and optical properties the LED chip and plastically sealed lamp were measured. Aging of the LED chip and lamp were performed under 70 degree Celsius and room temperature. Experiment results shown that there is no apparent effect of the native oxided AlAs layer and the process on the reliability of the LED devices.
Main application of 650nm band laser diodes are for digital versatile disk (DVD). We demonstrate here the 650nm AlGaInP LD grown by LP-MOCVD with the structure of selected buried ridge waveguide. Excellent performance of LD have been achieved such as threshold current, threshold current density as low as 20mA and 350A/cm2 respectively at room temperature, the operating temperature up to 90 for the linear power output of 5mw. RIN is about -130db/Hz, the samples of LD have been certified by PUH manufacturers.
KEYWORDS: Semiconducting wafers, Scanning electron microscopy, Quantum wells, Luminescence, Etching, Waveguides, Near field optics, Optical microcavities, Cladding, Atomic force microscopy
OPtical microdisk is based on circularly symmetric micro- resonator and featured of the 'whispering-galley' modes with high quality of factor Q. However, the non-preferred directional emission and lack of high output from the disk are its drawbacks for application. Recently, a remarkable advance in the novel deformed microdisk laser at middle-IR wavelength is highly attractive. In this report, as a preliminary try for microdisk at visible range, the InGaAlP quantum well circular cylindrical and deformed microdisks with radii about 2.5 to 10 micrometers emitting at wavelength of 0.62-0.67 micrometers were prepared by electron beam lithography and wet etching processing etc. The optical emission properties of these microdisks and studied by employing the scanning electron microscopy, atomic force microscopy, fluorescence image microspace and scanning near-field optical microscopy etc. The preferential emission in these deformed microdisks was visually observed. When the cross section of microdisk was gradually deformed from circle, the change of fluorescence image from uniform ring towards 2 or 4 favorable emission along the circumference of microdisks was confirmed. The deformation could be caused by either the shape or etching profile of the disk waveguide. In addition, the microdisks patterned with some microstructures were proposed.
High performance uncooled 1.55 micrometers InGaAsP/InP strained layer quantum well lasers grown by low pressure metal organic chemical vapor deposition (LP-MOCVD) were reported in this paper. Whole MOCVD over growth method were applied in this work. The threshold currents of 5 mA and the highest lasing temperature of 122 degree(s)C were obtained.
We have designed and fabricated the visible vertical-cavity surface-emitting lasers (VCSEL's) by using metalorganic vapor phase epitaxy. We use the 8(lambda) optical cavities with 3 quantum wells in AlGaInP/AlGaAs red VCSEL's to reduce the drift leakage current and enhance the model gain of AlGaInP active region. The structure has a p-type stack with 36 DBR pairs on the top and an n-type with 55-1/2 pairs on the bottom. Using micro-area reflectance spectrum, we try to get a better concordance between the center wavelength of DBR and the emitting wavelength of the active region. We used a component graded layer of 0.05(lambda) thick (x equals 0.5 approximately 0.9) at the p-type DBR AlGaAs/AlAs interface to reduce the resistance of p-type DBR. We use selective oxidation to define the current injection path. Because the oxidation rate of a thick layer is faster than a thinner one, we grown a thick AlAs layer close to the active region. In this way, we got a smaller active region for efficient confinement of injected carriers (the aperture area is 3 X 3 micrometers ) to reduce the threshold and, at the same time, a bigger conductive area in the DBR layers to reduce the resistance. WE employ Zn doping on the p-side of the junction to improve hole injection and control the Zn dopant diffusion to get proper p-i-n junction. At room temperature, pulse operation of the laser has been achieved with the low threshold current of 0.8 mA; the wavelength is about 670 nm.
Single mode 650 nm AlGaInP quantum well laser diodes grown by low pressure metal organic chemical vapor deposition was reported in this paper. Selected buried rigewaveguide were applied for single mode operation especially for DVD use. The operating temperature over 90 degree at CW output power 5 mW was achieved.
Liquid carbon tetrachloride (CCl4) was used as dopants for the growth of p-type GaAs and AlGaAs materials by low pressure metalorganic chemical vapor phase deposition. Heavily carbon doped (1.9 X 1020 cm-3) GaAs and high quality p-type Al0.3Ga0.7As materials were obtained. Several key growth parameters, such as growth temperature (560 degree(s)C - 725 degree(s)C), V/III ration (20 - 150) and CCl4 molecular flow (10-7 mol/min- 10-5 mol/min), were changed to investigate their influence on doping efficiency, growth rate and material properties. Electrochemistry capacity-voltage, Hall effect and photoluminescence methods were adopted to measure the electrical and optical properties. X ray double crystal diffraction method was used to study the relationships of carbon doping level and crystal lattice constant of epitaxial layers. On the basis of these research, carbon doped GaAs tunnel diode and high power GaAs/AlGaAs/InGaAs strain quantum well semiconductor laser structures were grown to qualify the carbon doped GaAs/AlGaAs materials comprehensively.
In this paper, we report on the design, growth and fabrication of 980 nm strained InGaAs quantum well lasers employing novel material system of Al-free active region and AlGaAs cladding layers. The use of AlGaAs cladding instead of InGaP provides potential advantages in laser structure design, improvement of surface morphology and laser performance. We demonstrate an optimized broad-waveguide structure for obtaining high power 980 nm quantum well lasers with low vertical beam divergence. The laser structure was grown by low-pressure metalorganic chemical vapor deposition, which exhibit a high internal quantum efficiency of approximately 90% and a low internal loss of 1.5 - 2.5 cm-1. The broad-area and ridge-waveguide laser devices are both fabricated. For 100 micrometers wide stripe lasers with cavity length of 800 micrometers , a low threshold current of 170 mA, a high slope efficiency of 1.0 W/A and high output power of more than 3.5 W are achieved. The temperature dependences of the threshold current and the emitting spectra demonstrate a very high characteristic temperature coefficient (T0) of 200 - 250 K and a wavelength shift coefficient of 0.34 nm/ degree(s)C. For 4 micrometers - width ridge waveguide structure laser devices, a maximum output power of 340 mW with COD-free thermal roll-over characteristics is obtained.
A novel coupled distributed Bragg reflector (DBR) with double thickness periods was theoretically analyzed based on the spontaneous radiation properties of high brightness AlGaInP light emitting diodes. Several important factors were considered including spontaneous radiation angle distribution, absorption and FTR of DBR. Calculation results showed that the optimum optical thickness of single layer of the DBR deviates from 1/4(lambda) . AlGaInP high brightness light emitting diodes both with Al0.5Ga0.5As/AlAs coupled DBR and with conventional DBR were fabricated by metalorganic chemical vapor deposition. X-ray double crystal diffraction and reflection spectrum were employed to determine the thickness and reflectivity of the DBR. It was found that reflectivity of coupled DBR is less sensitive to incident angle than conventional DBR, higher external quantum efficiency of light emitting diodes with coupled DBR was obtained than that with conventional DBR.
Orange AlGaInP high brightness light emitting diodes (LEDs) were fabricated by low pressure metalorganic chemical vapor deposition technology. AlGaInP double heterojunction structure was used as active layer. 15 pairs of Al0.5Ga0.5As/AlAs distributed Bragg reflector and 7 micrometers Al0.8Ga0.2As current spreading layer were employed to reduce the absorption of GaAs substrate and upper anode respectively. At 20 mA the LEDs emitting wavelength was between 600 - 610 nm with 18.3 nm FWHM, 0.45 mW radiation power and 1.7% external quantum efficiency. Brightness of the LED chips and LED lamps with 15 degree(s) viewing angle (2(theta) 1/2) reached 30 mcd and 1000 mcd respectively.
Low threshold current and high temperature operation of 650nm AlGaInP quantum well laser diodes grown by low pressure metal organic chemical vapor deposition are reported in this paper. 650nm laser diodes with threshold current as low as 22-24mA at room temperature, and the operating temperature over 90 degrees C at CW output power 5 mW were achieved in this study. These lasers are stable during 72 hours burn in under 5mW at 90 degrees C.
1.3 micrometers and 1.55 micrometers InGaAsP/InP quantum well (QW) light emitting diodes (LEDs) with narrow beam divergence grown by low pressure metal organic chemical vapor deposition are reported in this paper. 1.3 micrometers and 1.55 micrometers QW LEDs with beam divergence of 30 - 45 degree, chip output power of more than 300 (mu) W and 200 (mu) W, and single mode fiber output power of 60 (mu) W and 40 (mu) W were obtained by optimizing the device structure parameters.
High performance 1.3 micrometers and 1.55 micrometers InGaAsP/InP strained layer quantum well (SL-QW) lasers grown by low pressure metal organic chemical vapor deposition are reported in this paper. 1.3 micrometers SL-QW lasers and 1.55 micrometers SL-QW lasers with broad area threshold current densities as low as 400 A/cm2 and 450 A/cm2 (at cavity length 400 micrometers ), DC-PBH stripe device threshold currents of 5 approximately 10 mA and 6 approximately 10 mA were obtained, respectively. The prediction life time of 1.3 micrometers SL-QW lasers is more than 106 hrs at 25 degree(s)C, and degeneration activated energy is 0.682 eV according to the accelerate aging tests.
We have measured the reflectivity of self-pumped phase- conjugate (SPPC) mirror as a function of wavelength in the range between 720 nm and 830 nm in 0-degree-cut KNbO3:Ni. This is the longest wavelength for which the SPPC has been observed in KNbO3 at room temperature. We have obtained reflectivities R equals 43% at 725 nm and R equals 1% at 831.4 nm.
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