Applied Optics

Shack–Hartmann centroid detection method based on high dynamic range imaging and normalization techniques

Javier Vargas, Luis González-Fernandez, Juan Antonio Quiroga, Tomás Belenguer
In the optical quality measuring process of an optical system, including diamond-turning components, the use of a laser light source can produce an undesirable speckle effect in a Shack–Hartmann (SH) CCD sensor. This speckle noise can deteriorate the precision and accuracy of the wavefront ... [Appl. Opt. 49, 2409-2416 (2010)]

Effect of laser linewidth and fiber length on self-pulsing dynamics and output stabilization of single-mode Yb-doped double-clad fiber laser

Brahma�N. Upadhyaya, Antony Kuruvilla, Usha Chakravarty, Mangalpady�R. Shenoy, Krishna Thyagarajan, Shrikant�M. Oak
We report an experimental study of the effect of fiber length and laser linewidth on self-pulsing dynamics and output stabilization of a single-mode Yb-doped double-clad CW fiber laser. It is found that initiation of self-pulsing under low-level pumping conditions is due to relaxation oscillations ... [Appl. Opt. 49, 2316-2325 (2010)]

Numerical analysis of diameter influence on droplet fluorescence

Bruno Frackowiak, Cameron Tropea
Laser-induced fluorescence (LIF) is used in planar droplet sizing, assuming that the signal integrated over the droplet is proportional to its volume. Nevertheless, this assumption is rigorously valid in nonabsorbing mixtures. We performed an examination of the LIF signal with a fluorescence model, ... [Appl. Opt. 49, 2363-2370 (2010)]

Application of laser photofragmentation-resonance enhanced multiphoton ionization to ion mobility spectrometry

Jeffrey M. Headrick, Thomas A. Reichardt, Thomas B. Settersten, Ray P. Bambha, Dahv A. V. Kliner
We demonstrate detection of nitro-containing compounds with laser photofragmentation (PF) coupled with resonance enhanced multiphoton ionization (REMPI) and ion mobility spectrometry (IMS). In PF-REMPI, a laser dissociates the parent molecules, producing fragments that can then be ionized by ... [Appl. Opt. 49, 2204-2214 (2010)]

High-spatiotemporal-quality petawatt-class laser system

Hiromitsu Kiriyama, Mori Michiaki, Yoshiki Nakai, Takuya Shimomura, Hajime Sasao, Momoko Tanaka, Yoshihiro Ochi, Manabu Tanoue, Hajime Okada, Shuji Kondo, Shuhei Kanazawa, Akito Sagisaka, Izuru Daito, Daisuke Wakai, Fumitaka Sasao, Masayuki Suzuki, Hideyuki Kotakai, Kiminori Kondo, Akira Sugiyama, Sergei Bulanov, Paul R. Bolton, Hiroyuki Daido, Shunichi Kawanishi, John L. Collier, Cristina Hernandez-Gomez, Chris J. Hooker, Klaus Ertel, Toyoaki Kimura, Toshiki Tajima
We have developed a femtosecond high-intensity laser system that combines both Ti:sapphire chirped-pulse amplification (CPA) and optical parametric CPA (OPCPA) techniques and produces more than 30 J broadband output energy, indicating the potential for achieving peak powers in excess of 500 TW. ... [Appl. Opt. 49, 2105-2115 (2010)]

Phase errors due to speckles in laser fringe projection

Sara Rosendahl, Emil Hällstig, Per Gren, Mikael Sjödahl
When measuring a three-dimensional shape with triangulation and projected interference fringes it is of interest to reduce speckle contrast without destroying the coherence of the projected light. A moving aperture is used to suppress the speckles and thereby reduce the phase error in the fringe ... [Appl. Opt. 49, 2047-2053 (2010)]

Standoff detection of explosive substances at distances of up to 150 m

Anadi Mukherjee, Steven Von der Porten, C. Kumar N. Patel
We report detection and identification of trace quantities of explosives at standoff distances up to 150 m with high sensitivity (signal-to-noise ratio of ~70) and high selectivity. The technique involves illuminating the target object with laser radiation at a wavelength that is strongly absorbed ... [Appl. Opt. 49, 2072-2078 (2010)]

Laser smoothing of binary gratings and multilevel etched structures in fused silica

Krystian L. Wlodarczyk, Enrique Mendez, Howard J. Baker, Roy McBride, Denis R. Hall
We describe a promising approach to the processing of micro-optical components, where CO_2 laser irradiation in raster scan is used to generate localized surface melting of binary or multilevel structures on silica, fabricated by conventional reactive-ion etching. The technique is shown to provide ... [Appl. Opt. 49, 1997-2005 (2010)]

Comparison of a transmission grating spectrometer to a reflective grating spectrometer for standoff laser-induced breakdown spectroscopy measurements

Arel Weisberg, Joseph Craparo, Robert De Saro, Romuald Pawluczyk
We evaluate a new transmission grating spectrometer for standoff laser-induced breakdown spectroscopy (LIBS) measurements. LIBS spectra collected from standoff distances are often weak, with smaller peaks blending into the background and noise. Scattered light inside the spectrometer can also ... [Appl. Opt. 49, C200-C210 (2010)]

Relaxation oscillation in Er^3+-doped and Yb^3+/Er^3+co-doped fiber grating lasers

Lina Ma, Zhengliang Hu, Xun Liang, Zhou Meng, Yongming Hu
Relaxation oscillations in Er^3+-doped and Yb^3+/Er^3+ co-doped fiber grating lasers were investigated. Intensity noise models were established for both cases in which the fluctuations of pump power and cavity loss were analyzed. Simulation indicates that the relaxation oscillation is induced by ... [Appl. Opt. 49, 1979-1985 (2010)]

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