mW Maximum Output Power Research Articles

Nonlinear optical response and application of indirect narrow-bandgap SbTe nanosheets

The nonlinear optical properties of antimony telluride (SbTe) crystal with indirect narrow bandgap are investigated, which exhibits superior performance for nonlinear laser modulation in the infrared band. The nonlinear optical coefficients of SbTe nanosheets are determined to be −3.3 cm/GW, −2.3 cm/GW, −1.9 cm/GW and the modulation depths are 5.5 %, 2.0 %, 1.5 % at 400 nm, 800 nm, 1064 nm, respectively. Based on the SbTe-SA, a Yb:GdScO3 laser centered at 1064 nm is achieved with 633 mW maximum output power, 56 fs pulse width and 104 MHz repetition rate. The damage threshold of the SbTe nanosheets is calculated to be exceed 338 GW/cm2, revealing the great potential in high-power laser modulation. This investigation marks the inaugural theoretical and experimental analysis of SbTe’s optical properties and its application in laser modulation, laying the groundwork for future research into indirect narrow-bandgap materials in laser technology.

High-Efficiency GaN/SiC Doubler Terahertz Monolithic Integrated Circuit at 175 GHz

A high-power, high-efficiency, 175 GHz frequency doubler terahertz monolithic integrated circuit (TMIC) in continuous wave (CW) mode has been fabricated using planar gallium nitride (GaN) Schottky barrier diodes (SBDs) on a SiC substrate. Heat dissipation is improved by adopting a high thermal conductivity SiC substrate. At room temperature, the GaN doubler has an output power exceeding 110 mW at 164 GHz to 181 GHz with an efficiency of 11 % to 20.6 % in CW mode. A 242 mW maximum output power with 20.2 % efficiency is obtained at 175 GHz. The results imply that a GaN-based monolithic integrated frequency doubler provides a viable means of obtaining high output power and high efficiency in CW mode.

Long-term stable 850-Hz linewidth single-longitudinal-mode ring cavity fiber laser using polarization-maintaining fiber

A long-term stable single-longitudinal-mode (SLM) all polarization-maintaining (PM) compound-ring cavity fiber laser is reported. The results show that the PM fiber's strong ability to resist the environment disturbance allows finely designing the length of each secondary cavity in real time according to the main cavity under the laboratory environment, and then the effective longitudinal mode spacing can be sufficiently increased by accurately using the Vernier effect, so that the mode-hopping can be effectively suppressed. Furthermore, the temperature compensation is used for asynchronously fine-adjusting each cavity length to follow the Vernier effect requirement more strictly. The mode-hopping-free SLM operation time of the packaged laser reaches 11 h. As far as we know, this is the longest SLM free running time of ring cavity fiber laser to date. The optical signal to noise ratio of the laser reaches 77 dB and the linewidth is less than 850 Hz with up to 50 mW maximum output power.

Experimental and theoretical investigations on high power vacuum-ultraviolet laser at 165 nm by eighth-harmonic generation in KBBF

A high power nanosecond (ns) vacuum-ultraviolet (VUV) laser at 165 nm was demonstrated by means of a frequency-octupled 1319 nm Nd:YAG laser with a thick KBe2BO3F2 crystal. A 6.8 mW maximum output power at 165 nm was attained in the experiment, which is to our knowledge the highest power for all solid state lasers below 170 nm. The 165 nm output power versus the 330 nm pump power was simulated. The calculated result was well consistent with experimental data. Meanwhile, the dependence of 165 nm output power on the KBBF effective length was investigated theoretically. It was found that the thickness of KBBF crystal used in our experiment is close to the optimal thickness, which allows to creating the high VUV output power. We used the simulation further to analyze the pulse width, beam quality factor and beam spatial intensity profile of the generated 165 nm radiation.

Noise-like pulses generated from a passively mode-locked fiber laser with a WS2 saturable absorber on microfiber

We report on a noise-like pulse (NLP) generation in a mode-locked erbium-doped all-fiber laser using a WS2-deposited microfiber saturable absorber (SA). The prepared WS2 SA can serve as an excellent mode-locked and highly nonlinear device in the all-fiber laser cavity. At proper pump power and polarization states, typical NLPs can be generated. Adjusting the polarization also yields special NLPs with second-order harmonic mode-locking. For typical NLPs, 37 mW maximum output power and 8.8 nJ pulse energy are achieved at 334 mW pump power. The microfiber-based WS2 component could be a potential device for exploring nonlinear dynamics, such as NLPs.

Single-Stage Frequency Quadrupler With SBD and Four-Octave LPF at 335 GHz

This paper presents designs of a single-stage quadrupler at 340 GHz based on Schottky varactors with 7 mW maximum output power. The Schottky diode model is invented to improve the accuracy of design, which considers the behaviors of current–voltage ( I / V ), capacitance–voltage ( C / V ), plasma resonance, self-heating effect, and skin effect of Schottky diodes under deep driven situation into consideration. Compact suspended microstrip resonators (CSMRs) are adopted as harmonic rejection structure with minimized length/width ratio and shorted idlers at both the second and third harmonics. The measurement results indicate that the CSMR low-pass filter has stopband bandwidth of more than four-octave, whose S12 <−10 dB within 140–385 GHz and S11 <−10 dB below 95 GHz. The measured quadrupler output power is above 1 mW at 322–345 GHz, and the measured peak efficiency achieves above 4.2% at 339.2 GHz with 100 mW driven power.

Crystal growth, spectroscopic characterization, and sub-100 femtosecond mode-locked operation of a Yb:LiLuF_4 laser

We present a comprehensive growth, spectroscopic, and laser performance investigation of a Yb:LiLuF4 crystal, including CW laser experiments, and, for the first time to the best of our knowledge, mode-locked laser operation. Pumping with two 400 mW, polarization-combined, single-mode fiber-coupled laser diodes, we demonstrated efficient CW emission with 140 mW maximum output power and up to 59% slope efficiency. Using a semiconductor saturable absorber mirror for inducing the mode-locked regime and a pair of fused silica prisms for intracavity group delay dispersion compensation, we obtained soliton mode-locking pulses with 90 fs duration for the emission with polarization parallel to the crystal c-axis and 113 fs for the orthogonal polarization, with average power exceeding 30 mW in both cases at about a 90 MHz repetition rate.

Controllable high-power, variable-frequency CMOS circuit for microactuator applications

A large-output power, high-current high-voltage, CMOS driving circuit for electrothermal microactuators is presented in this work. The circuit addresses the challenge of providing microelectromechanical systems devices with a monolithic integrated circuit that is capable of outputting high voltage with low output resistance that matches the actuator load for maximum power transfer. The circuit is implemented using a modified eight-stage charge pump. A digital control logic is designed to control the working charge pump stages in order have a variable output voltage between 4 and 15.5 V on a load producing about 150 mW maximum output power. To the authors’ knowledge, the circuit’s output resistance is the lowest among charge pumps that are capable of producing such high voltages. An AC pulse output of 15.5 V amplitude and variable frequency between 60 and 2000 Hz is included in the circuit. The circuit is operated by a conventional 5 V supply. With the variable DC output voltage level and AC output capability, the circuit is suitable for driving many electrothermal microactuators. The total size of the chip excluding pads is 5 mm2.

Innovations and Challenges by Applying Sublingual Laser Blood Irradiation in Juvenile Idiopathic Arthritis

Sublingual laser blood irradiation (SLBI) was applied into a randomized, single-blind, placebo-controlled study in juvenile idiopathic arthritis (JIA), aimed at inducing disease remission. 105 children with JIA, without an adequate response to classical treatment, were administrated a disease modifying drug (Methotrexate) and were randomly assigned to three groups. Group I (36 patients) received SLBI with the Weberneedle Lasershower Mouth Applicator with three wavelengths (635 nm, 536 nm, and 405 nm), 5 mW maximum output power each, in continuous mode, simultaneously, for 20 minutes daily, 7 successive sessions per month, repeated every 7 weeks, for three times. Group II (36 patients) received placebo SLBI. Group III (33 patients) received only treatment with Methotrexate. Evaluation was performed using American College of Rheumatology Pediatric criteria (ACR Pedi) at study enrollment and at 8, 16, 24, and 48 weeks. At the end of study, there was an improvement of the ACR Pedi 30 by 86.11% in SLBI group compared to only 61.11% in Group II, respectively, and 60.6% in Group III (P=0.001), with significant statistical differences. SLBI has reduced the pain, lowered the number of articulations with movement limitation, increased the quality of life, and made it possible to avoid the administration of biological agents.

High efficiency tandem-pumped fiber amplifier

A 1020 nm fiber laser is designed based on fiber Bragg grating and then its output power is boosted to 590 mW through a two-stage amplifier. A tandem pumping fiber amplifier is constructed with the 1020 nm laser used as a pump source. The output power and the efficiency of the amplifier are measured with different lengths of gain fiber. A 385 mW maximum output power with an 81% slope-efficiency is achieved when the gain fiber is 8.5 m. The output power and the efficiency of a traditional amplifier in which 976 nm diode laser is used as a pump source are also measured. The experimental results indicate that tandem pumping fiber amplifier can achieve a higher efficiency than traditional fiber amplifier.

Development of both-side junction silicon space solar cells

This paper reports the recent results of improving the radiation hardness of silicon solar cells, which is SHARP and NASDA's project since 1998 (Tonomura et al., Second World Conference on Photovoltaic Solar Energy, 1998, pp. 3511–3514). Newly developed 2×2 cm 2 Si solar cells with ultrathin substrates and both-side junction (BJ) structure showed 72.0 mW (13.3% efficiency) maximum output power at AM0, 28°C after 1 MeV electron irradiation up to 1×10 15 e/cm 2 and the best cell showed 72.5 mW (13.4%) maximum output power. These solar cells have p–n junctions at both front and rear surfaces and showed less radiation degradation and better remaining factor than previous solar cells.

BENEFICIAL EFFCTS OF LASER THERAPY IN THE EARLY STAGES OF RHEUMATOID ARTHRITIS ONSET

The purpose of this study was to determine the effects of laser therapy in pain reduction and/or recovery of patients at the onset of Rheumatoid Arthritis (RA), comparatively with the traditional nonsteroidal anti-inflammatory drugs (NSAIDs). Fifty-nine patients with RA of 6-12 months duration were included in the study. The patients were divided into 3 groups: Group 1 (21 patients) received laser therapy; Group 2 (18 patients) was submitted to placebo laser therapy and NSAIDs medication; Group 3 (20 patients) was treated only with NSAIDs. Physical therapy was instituted in all three groups. GaAIAs diode laser of 830 nm wavelength and 200 mW maximum output power was used. Group 1 received laser therapy once each day, eight days per month, for a total of 32 treatments during a four-month period. The parameters used were 2-4 J/cm2 energy density, and a frequency of 5 Hz or 10 Hz depending on the number and severity of pain in the affected joints. Placebo laser treatment was given to group 2. The functional activity score, the acute phase reactants (ESR and C - reactive protein), T - lymphocytes and NK (natural killer) - cells were estimated. Synovial biopsies and Magnetic Resonance Imaging (MRI) of the synovial membrane were performed as well. The analysis of the clinical and biological parameters at the end of treatment showed a statistically significant decrease of duration of morning stiffness, of pain at rest and during movements, and improved acute phase reactants. The overall efficacy rate in these studies was 86% in the fttst group, 50% in laser placebo group and 40% in the NSAIDs-treated third group. After four months of treatment, our investigations showed that 830 nm infrared laser therapy promoted the restoration of function, relieved pain and limited the complications of RA.

High-efficiency lasing at 810 nm in single-mode &lt;inline-formula&gt;&lt;roman&gt;Tm&lt;/roman&gt;&lt;sup&gt;&lt;roman&gt;3+&lt;/roman&gt;&lt;/sup&gt;&lt;/inline-formula&gt; doped fluorozirconate fiber pumped at 778 nm

We report a Tm3+ doped fluorozirconate fiber laser suitable for the first telecommunications window. We present a mathematical model and experimental measurements. The cw, low threshold pump power of 15 mW, pumped by a Ti:sapphire laser at 778 nm, and a 85 mW maximum output power around 810 nm with a 85% slope efficiency against launched pump power are achieved. This represents a conversion efficiency of ~95%, which is the highest reported to date for any laser. Visible up-conversion fluorescence is also observed. We describe two different oscillator configurations.

Flip-chip bonded 0.85-μm bottom-emitting vertical-cavity laser array on an AlGaAs substrate

We report high-performance 0.85-μm bottom-emitting vertical-cavity surface-emitting lasers (VCSELs) on an AlGaAs substrate with 2.1 mA threshold current density 4.2 mW maximum output power, 11.7% power conversion efficiency and a maximum operating temperature of 130/spl deg/C. We also demonstrate a flip-chip bonded 0.85-μm bottom-emitting VCSEL array, and confirm all pixels across the 8×8 VCSEL array operate at a f <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> dB bandwidth of 2.6 GHz at only 4.2 mA.

High power top-surface emitting oxide confined vertical-cavitylaser diodes

Large area MBE grown vertical-cavity surface emitting laser diodes (VCSELs) for high power emission at ~980 nm wavelength have been fabricated. Top emitting devices of 146 µm active diameter deliver 160 mW at 20% wallplug efficiency and 180 mW maximum output power in a junction-up configuration.

High efficiency selectively oxidised MBE grown vertical-cavitysurface-emitting lasers

The authors have used conventional solid source MBE with Be p-type doping and single layer selective oxidation to produce 20 /spl mu/m diameter VCSELs (/spl lambda/=980 nm) with 47% wallplug efficiency at 10 mW output power and over 40 mW maximum output power in a configuration without heatsinking.

Temperature-dependent characteristics and single-mode performance of AlGaInP-based 670-690-nm vertical-cavity surface-emitting lasers

We report on temperature dependent characteristics and single mode performance of one-wave cavity, planar implanted, AlGaInP-based vertical-cavity surface emitting lasers. By optimizing the overlap between the gain peak and the cavity mode of the structure, we demonstrate record device performance, including 8.2 mW maximum output power and 11% power conversion efficiency for multimode operation and 1.9 mW and 9.6% power conversion efficiency for single mode operation at 687 nm. Improved performance at elevated temperatures is also achieved, with 1.5 mW output power demonstrated at 50/spl deg/C from a 15-μm-diameter device.

High performance InGaAs/GaAlAs laser diodes for electronic/photonic integrated circuit applications

High-performance, short-cavity, strained-layer InGaAs/GaAlAs laser diodes that are suitable for two-dimensional electronic-photonic integrated circuit (EPIC) applications have been demonstrated. Continuous-wave threshold currents as low as 4 mA, and singlemode output powers in excess of 100 mW (maximum output power: 120 mW) were achieved for as-cleaved, reactive-ion-etched, 3.5 μm-wide, 200 μm-long, InGaAs/GaAlAs ridge-waveguide laser diodes in the junction-side up configuration.

Reliable High-Power Operation of InGaAlP Visible Light Laser Diodes with Strained Active Layer

Reliable high-power operation of transverse-mode stabilized InGaAlP laser diodes has been achieved with a selectively buried ridge waveguide (SBR) structure and a very thin (150 Å) In0.62Ga0.38P active layer. A strained In0.62Ga0.38P layer was employed in order to improve the temperature characteristics during high-power operation. An over 100 mW maximum output power was obtained. Operation current density was found to have a large effect on the device reliability. Lasers with a long cavity operate in a low current density, resulting in an increase in device lifetime. In the 600 µm long SBR lasers, stable continuous wave (CW) operation exceeding 1000 hours has been achieved with a 30 mW output at 50°C.

Low-threshold, high-power, single-longitudinal-mode operation in 1.5μm multiple-quantum-well, distributed-feedback laser diodes

Extremely low-threshold, single-longitudinal-mode operation is reported for 1.5μm band Gain As multiple quantum well, distributed feedback laser diodes. A 5.5 mA minimum threshold current as well as 40 mW maximum light output power and 0–33 W/A maximum quantum efficiency have been attained under CW condition at room temperature.