• Current Optics and Photonics
• /
• v.2 no.5
• /
• pp.443-447
• /
• 2018

We propose a diode-pumped cesium laser using frequency locking of a pump laser that can effectively increase the maximum output power of the cesium laser. We simultaneously monitored the absorption spectrum of cesium and the laser output power, and the frequency of pump laser was locked at the center of the $D_2$ absorption line of the cesium atom to obtain an effective gain enhancement. Using this scheme, we have achieved output power increase of ~0.1 W compared to when frequency locking was not applied. Furthermore, by optimizing the temperature of the cesium cell and the reflectivity of the output coupler, we successfully achieved an output power of 1.4 W using the pump power of 2.9 W, providing a slope efficiency of 61.5% and optical-to-optical efficiency of 49%.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.4C no.3
• /
• pp.96-100
• /
• 2004

The Nd： YAG laser is commonly used throughout many fields such as accurate material processing, IC marking, semiconductor annealing, medical operation devices, etc., due to the fact that it has good thermal and mechanical properties and is easy to maintain. In materials processing, it is essential to vary the laser power density for specific materials. The laser power density can be mainly controlled by the current pulse width and pulse repetition rate. It is important to control the laser energy in those fields using a pulsed laser. In this paper we propose the constant-frequency current resonant half-bridge converter and monitoring of capacitor charging voltage. This laser power supply is designed and fabricated to have less switching loss, compact size, isolation with primary and secondary transformers, and detection of capacitor charging voltage. Also, the output stabilization characteristics of this Nd： YAG laser system are investigated. The test results are described as a function of laser output energy and flashlamp arc discharging constant. At the energy storage capacitor charges constant voltage, the laser output power is 2.3％ error range in 600[V].

• The Journal of Korean Medicine Ophthalmology and Otolaryngology and Dermatology
• /
• v.27 no.2
• /
• pp.33-50
• /
• 2014

Objective : The purpose of this study is to analyze research trends on laser output used for treatment of hair loss. Methods : We searched papers using Pubmed, NDSL, KISS, and RISS. First search used the keyword "Laser, Alopecia" in Pubmed. Inclusion criteria were last 15 years, English, related to output. Finally we searched papers using the keyword "Laser and Alopecia" in NDSL, KISS, and RISS. Inclusion criteria were the same as first research except for English. Results : A total of 43 studies were found, 28 studies were excluded and 15 studies were selected and analyzed. And of the 15 studies, 7 studies were foreign papers and 8 studies were domestic papers on clinical application of laser status. Mainly Used type of laser was a diode laser. As a result, we found that treatment group had more improvement than control group. The range of the laser-output was 1mW-150W in Alopecia laser therapy. Conclusions : Low-level (LLLT) as well as High-level laser therapy (HLLT) can be effectively used as an alternative to the treatment of alopecia. Thus, further attention and studies are needed on this topic in order to reduce the side effects and demonstrate the effectiveness clearly.

• Korean Journal of Optics and Photonics
• /
• v.19 no.4
• /
• pp.320-326
• /
• 2008

The output characteristics of a laser-diode pumped electrooptic Q-switched Nd:YAG ceramic laser were investigated. The output energy of a Q-switched Nd:YAG ceramic laser was optimized under an output coupler reflectivity of 77%, a laser-diode pulse width of $1,000\;{\mu}s$, and a delay time of $985\;{\mu}s$. The output energy of the Q-switched pulse was measured to be 0.35 mJ with a pulse width of 4 ns under a pump energy of 17.9 mJ. The output efficiency and the peak power were 1.9% and 87.5 kW, respectively.

• Journal of the Optical Society of Korea
• /
• v.12 no.1
• /
• pp.31-37
• /
• 2008

To increase output power of a He-Ne laser we propose to use the capacitive rf discharge and implement four channel structure. Most of experiments were carried out with a single laser tube from this structure to optimize the output mirror transmission, pressure and composition of the mixture. A laser tube of 2.8 mm inner diameter and 50 cm discharge length can give an output power of above 5.5 mW at 3.39 ${\mu}m$. Four such tubes in "matrix" structure let us obtain 20 mW of output. Simplified models which can be used to evaluate the behavior of an equivalent electrical circuit with laser plasma and qualitative characteristics of output power of He-Ne laser were also described.

• Journal of the Optical Society of Korea
• /
• v.6 no.2
• /
• pp.48-54
• /
• 2002

Experimental study is performed on flashlamp-pumped Ti: sapphire lasers with single, double, and four-partial-ellipse-pump cavities aiming at improving the performance of the lasers. The output energy of 604 mJ per pulse with a width of 25 $\mu$s at a total laser efficiency of 0.13% is achieved in the laser pumped by a light pulse of 45$\mu$s without a fluorescent converter The laser output energy versus its Ti: sappy ire rod length, pumping-light pulse duration, and electrical input energy are discussed with or without using a fluorescent converter. The result shows that much more output energy is obtained il a longer Ti: sapphire-rod laser pumped by a shorter light pulse when its output coupler has an optimized transmittance. In addition, an enhancement of output energy by a factor of 7 is achieved. in the laser using a fluorescent converter LD490.

• Current Optics and Photonics
• /
• v.4 no.4
• /
• pp.273-276
• /
• 2020

We report on the relationship between output current for quadrant photodetector (QPD) and bias voltage in silicon-based p-i-n (positive-intrinsic-negative) QPD examined using millisecond pulse laser (ms pulse laser) irradiation. The mechanism governing the relationship was further studied experimentally. The output current curves were obtained by carrying out QPD under different bias voltages (0-40 V) irradiated by ms pulse laser. Compared to other photodetectors, the relaxation was created in the output current for QPD which is never present in other photodetectors, such as PIN and avalanche photodetector (APD), and the maximum value of relaxation was from 6.8 to 38.0 ㎂, the amplitude of relaxation increases with bias value. The mechanism behind this relaxation phenomenon can be ascribed to the bias voltage induced Joule heating effect. With bias voltage increasing, the temperature in a QPD device will increase accordingly, which makes carriers in a QPD move more dramatically, and thus leads to the formation of such relaxation.

• Laser Solutions
• /
• v.2 no.2
• /
• pp.42-51
• /
• 1999

This study has been performed to investigate into some effects of the output power and traverse speed of laser beam on the microstructures, hardness and fatigue resistance of the ductile iron surface-hardened by $CO_2$ laser defocussed beam. Optical micrographs have shown that with increasing the output power and decreasing the traverse speed, the martensite was coarsened and some retained austenite were appeared in ductile iron. The microstructures of hardening zone were composed of bull's eye and some nodular graphite dissolved structures by the effect of self quenching. Fatigue fracture characteristics of ductile iron have appeared in the high stress and low stress ranges. The fracture initiated at nodular graphites in the surface hardened layer due to the stress concentration caused by a notch effect. The interior graphite nodules were broken away or popped out during crack propagation. Fatigue test has shown that values of fatigue strength considerably increased with increasing output power at a given traverse speed.

• Korean Journal of Optics and Photonics
• /
• v.12 no.6
• /
• pp.489-495
• /
• 2001

We developed a design code for a diode side-pumped Nd:YAG laser with a diffusive reflector to investigate the optimum design conditions resulting in homogeneous absorption distribution and efficient laser output power. By including the thermal tensing effect in the calculation of the laser output power, the calculated output powers were in fairly good agreement with the experimental results within the stable resonator condition. The calculation method can be used effectively for a diode side-pumped Nd:YAG laser in choosing the optimum design parameters and in predicting the laser output power.

• Korean Journal of Optics and Photonics
• /
• v.17 no.5
• /
• pp.455-460
• /
• 2006

The output characteristics of a ceramic Nd:YAC laser pumped by a fiber-coupled laser diode was investigated. An efficiency and a slope efficiency of 33.8 % and 39.3 % respectively were obtained, under an output coupler reflectance of 90.4 %. The laser power has decreased suddenly due to the thermal tensing effect more than 6 W pumping powers.