Frequency-doubled Solid-state Lasers Research Articles

CW molecular iodine laser pumped with a low power DPSSL

Cw oscillation of molecular iodine on many lines in the range of 557–802 nm pumped with a low power common diode pumped and frequency doubled solid state laser DPSSL is reported. The DPSSL is temperature stabilized, operates in single frequency and can be tuned by about 2 nm at 532 nm. Operation conditions of this simple and low cost iodine ring laser will be described and possible applications will be discussed.

Method of analyzing silicon groove damage using QSS‐PC, PL imaging, silicon etch rate, and visual microscopy for solar cell fabrication

AbstractThis work uses a variety of tools to investigate damage caused by laser and dicing saw grooving in silicon. The tools comprise quasi steady state photoconductance decay, photoluminescence imaging, measurement of silicon etch rate in anisotropic etch solution, and visual microscopy. Shallow grooves were formed using a 532 nm Q‐switched Nd:YLF frequency doubled solid state laser and a high speed spindle dicing saw. Combined analysis of the characterization tools enabled determination of the damage radius of the grooves within the bulk of the wafer, the radius of damage in the dielectric layer laterally along the surface of the wafer, as well as the groove etching requirements to fully recover the minority carrier lifetime in the vicinity of the groove. Copyright © 2011 John Wiley & Sons, Ltd.

Pain Perception at Laser Treatment of Peripheral Retinal Degenerations With Green and Infrared Wavelengths

To compare the pain perception at laser treatment of peripheral retinal degenerations with green (532-nm) and infrared (810-nm) wavelengths. Prospective randomized clinical trial. Sequential patients with indications for photocoagulation of bilateral peripheral retinal degenerations were invited to participate in the study. Thirty patients (60 eyes) were enrolled in the study. Each patient had 1 eye treated with infrared laser (diode, 810-nm wavelength) and the other eye treated with green laser (frequency-doubled solid-state laser, diode-pumped, with 532-nm wavelength). The eyes were randomized to infrared or green wavelengths. The right eye was the first treated in all cases regardless of the wavelength arrangement. Immediately after photocoagulation of each eye, the patient was asked to grade pain perception according to an 11-point (ie, 0-10) numerical rating scale (NRS), with 0 meaning "No pain" and 10 meaning "Pain as bad as you can imagine." The primary outcome was the assessment of pain. The mean grading of pain perception was 2.80 (SD 1.27; mode and median = 2) to green wavelengths and 5.07 (SD 1.36; mode = 4 and median = 5) to infrared wavelengths (P < .001). The results showed a statistically and clinically significant difference of pain perception between the 2 groups, with advantage to the green laser group.

Efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity

To report the efficacy and safety of green laser photocoagulation for threshold retinopathy of prematurity (ROP). We reviewed the clinical records of the neonates who had undergone green laser photocoagulation for threshold ROP at the Federal University of Pernambuco in Brazil between January 2004 and January 2006. All procedures were conducted with local anesthetic drops. The neonates were monitored throughout the procedure by a neonatologist. A frequency-doubled solid state laser, diode-pumped, with 532 nm wavelength was used. The presence of tunica vasculosa lentis or cataract were excluded before laser treatment. The following preoperative data were obtained for each patient: age, birth weight and the grade of ROP. Postoperative data included complications associated with the laser treatment, grade of ROP and evaluation whether further surgery was necessary due to failure of laser photocoagulation. Twenty-two neonates underwent photocoagulation with green laser for threshold ROP. A total of 31 eyes were included in the study. The mean gestational age was 30 +/- 3 weeks and the mean birth weight was 1120 +/- 490 g. Regression of the disease after laser therapy was observed in 30 eyes (96.7%). Despite treatment one eye presented stage 4A. Only 7 eyes required repetitive laser therapy. No adverse effects such as burning anterior segment tissues or bleeding in the anterior chamber occurred. No posterior segment side-effects were observed. Cataract formation was not observed at the last follow-up examination. Green laser photocoagulation remains an effective and safe alternative to red laser photocoagulation and to cryotherapy in the treatment of threshold ROP.

Control of the radiation parameters of an intracavity frequency-doubled solid-state laser by means of optoelectronic feedback

A method for chaotic oscillation suppression in intracavity frequency-doubled lasers based on the rate-equation model of a bipolarised solid-state laser is proposed. It is shown that the use of optoelectronic feedback either stabilises the system in the stationary state or leads to quasi-sinusoidal oscillations with a constant amplitude.

Q-Switched Intracavity Frequency-Doubled Solid State Lasers: Influence of ETU Effect, Repetition Rate and ESA Effect

Our theoretical analysis showed that the overall intracavity frequency-doubled actively Q-switched solid state laser performance is affected by both pulse repetition rate and energy transfer up-conversion effect. The energy transfer up-conversion effect increased greatly and seriously degraded the laser performance especially when operating at high pumping power and low pulse repetition rate. The curves generated by numerical computation of the presented model can be used to predict the laser performance. We concluded that the pulse lengthening effect also appears with the influence of energy transfer up-conversion and is not related to the repetition rate. From the analysis, we found that the frequency doubling coefficient that Liu and Kim chose in their experiment was just the optimized value. Considering the effect of excited state absorption of saturable absorber into passively Q-switched intracavity frequency doubled solid state laser, the second threshold condition for this model is derived. A simple and very clear formula is obtained.

Modeling of active and passive Q-switched intracavity frequency-doubled solid state lasers

We present a model of high-power continuous-wave laser-diode pumped actively Q-switched intracavity frequency-doubled green laser, in which the energy transfer up-conversion effect was taken into account. Our theoretical analysis showed that the overall laser performance is affected by both pulse repetition rate and energy transfer up-conversion effect. The energy transfer up-conversion effect increase greatly and seriously degrade the laser performance especially when operating at high pumping power and low pulse repetition rate. The good agreement with the experimental measurements reported in previous paper demonstrates that energy transfer up-conversion effect have to be considered to predict the laser operational characteristics accurately. We also first derived the second threshold condition for passively Q-switched intracavity frequency doubled solid state laser by including the effect of excited state absorption of saturable absorber into this model. A simple, and very clear formula was obtained.

High-Power, Continuous-wave and Blue Light Generation by Intracavity Frequency Doubling of a Cr:LiSrAlF6 Laser

Thermal quenching phenomena in a Cr doped LiSrAlF6 (Cr:LiSAF) laser pumped by a laser diode (LD) was studied to improve the second harmonic generation (SHG). The second harmonic to obtain blue light was generated by an intracavity frequency doubled solid state laser where LiB3O5 (LBO) crystal was inserted in the cavity. A circular pumping beam profile was essential to suppress thermal quenching, which was realized by the arrangement of horizontal and vertical two LD pumping or bundled fiber pumping. In particular for the latter case, blue light of 120 mW was obtained with pump power of 1200 mW.