Lawrence Shah | University of Central Florida (original) (raw)
Papers by Lawrence Shah
Laser Technology for Defense and Security V, 2009
We have designed and developed a grating based thulium (Tm) doped fiber laser with ~150 nm tuning... more We have designed and developed a grating based thulium (Tm) doped fiber laser with ~150 nm tuning range which is used as the master oscillator in a master oscillator power amplifier (MOPA) thulium fiber laser system. Due to thermal instability in the grating used for tuning, the MO could produce a power up to 4.5 W, beyond which the oscillator
Advanced Solid-State Lasers, 2002
ABSTRACT © 2002 Optical Society of America
Summaries of Papers Presented at the Lasers and Electro-Optics. CLEO '02. Technical Diges, 2002
... Mysyrow-Miura, J. Qiu, K. Hirao, Anomalous icz, Writing of permanent birefringent mi-anisot... more ... Mysyrow-Miura, J. Qiu, K. Hirao, Anomalous icz, Writing of permanent birefringent mi-anisotropic light scattering in Ge-doped sil-crolayers in ... Fabrication of Waveguides and Gratings in Chalcogenide Thin Films A. Zoubir, L. Shah, MC Richardson, C. Rivero, C. Lopez and KA ...
Guided mode resonance filters produced a stable spectrally narrow Thulium fiber laser, at ~1985 n... more Guided mode resonance filters produced a stable spectrally narrow Thulium fiber laser, at ~1985 nm. Laser spectral linewidths of 10-30 pm with a slope efficiency of ~35% were demonstrated. Spectral reflectivity was explored and showed 0.4-1.0 nm FWHM.
Journal of Laser Micro/Nanoengineering, 2006
The need for improved precision in a wide variety of micromachining applications has driven scien... more The need for improved precision in a wide variety of micromachining applications has driven scientific interest in ultrashort pulse lasers. Despite numerous demonstrations of reduced heat effect and improved processing quality, the utility of such lasers has been limited by the heavy demands placed upon laser performance. In addition to high contrast laser pulses with minimal pulse-to-pulse fluctuation, an ultrashort pulse laser must provide near diffraction-limited beam quality and robust long-term laser operation with high repetition rate for high processing speeds. We report here on a research prototype, high power femtosecond fiber chirped pulse amplification system. The system produces compressed pulses with energies >50 µJ at >15 W with M 2 <1.4. The use of cubicon pulses, i.e. stretched pulses with cubical spectral and temporal shape, enables pulse compression to <500 fs with >1000:1 temporal contrast despite significant self-phase modulation during amplification corresponding to a nonlinear phase delay of ~6π. As a demonstration of high speed femtosecond micromachining, we drill and cut 0.5-mm thick metal, semiconductor and dielectric targets.
Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class... more Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class of laser materials that can be used as both a laser host and a nonlinear frequency converter. Laser action and self-frequency doubling (SFD) has been observed with both 10% and 20% Yb3+-doped YCOB crystals. Laser operation was obtained in a hemispherical linear cavity,
Development of the oxyborate Nd3+:YCOB has brought about the realization of single crystal elemen... more Development of the oxyborate Nd3+:YCOB has brought about the realization of single crystal elements under diode pumped operation for compact simple, solid state lasers producing visible laser emission. Efficient laser action and self-frequency doubling (SFD) has been obtained for both Ti:Sapphire and diode pumped operations. Comparable results were obtained for a hemispherical linear cavity with a 2% output coupler for
Abstract: We present an Yb:YAG thin-disk oscillator providing a tunable linewidth of 50-pm via VB... more Abstract: We present an Yb:YAG thin-disk oscillator providing a tunable linewidth of 50-pm via VBG-based feedback. Output powers of up to 2 W have been recorded while maintaining an excellent spatial profile. © 2011 Optical Society of America OCIS codes: (140.0140) ...
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Abstract A system for multi-kilometer atmospheric propagation experiments including a master osci... more Abstract A system for multi-kilometer atmospheric propagation experiments including a master oscillator with~ 108 nm tunability and a power amplifier tested as an oscillator with~ 58% slope efficiency and stable 200 W output power is discussed.
The generation of stretched 20 pJ pulses with 200 kW peak power is demonstrated in an in-line Yb ... more The generation of stretched 20 pJ pulses with 200 kW peak power is demonstrated in an in-line Yb fiber chirped pulse amplification system at a repetition rate of 50 kHz. The pulses are compressible down to 400 fs using nonlinear cubical dispersion compensation.
Applied Physics A-materials Science & Processing, 2003
We describe several approaches to basic femtosecond machining and materials processing that shoul... more We describe several approaches to basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high-throughput deep hole drilling in glasses in ambient air, and precision highspeed micron-scale surface modification of composite materials and chalcogenide glasses. Ablation of soda-lime silicate glass and PbO lead-silicate is studied under three different sets of exposure conditions, for which both the wavelength and pulse duration are varied. Ablation rates are measured below and above the air ionization threshold. The differences observed are explained in terms of self-channeling in the ablated hole. Fabrication of practical devices such as waveguides and gratings is demonstrated in chalcogenide glass.
We describe several scenarios of basic femtosecond machining and materials processing that should... more We describe several scenarios of basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high through-put deep hole drilling in polymers and glasses in ambient air, and precision high speed micron-scale surface modification of materials.
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIII, 2014
ABSTRACT We present the characterization of thermal distortion induced in bulk and orientation-pa... more ABSTRACT We present the characterization of thermal distortion induced in bulk and orientation-patterned GaAs samples by a 100 W narrow linewidth, linearly polarized CW Tm:fiber laser focused to ~150 μm diameter. For a 500-μm thick bulk GaAs sample, the induced thermal distortion is measured using a probe laser beam at 1080 nm and a Shack-Hartmann wavefront sensor (SHWS). We also compare the power dependent induced divergence for 500-μm thick bulk GaAs and 10-mm thick orientation-partnered GaAs (OP-GaAs) samples as they are translated axially through the focus of a 2-μm wavelength Tm:fiber laser beam.
Proceedings of SPIE - The International Society for Optical Engineering, 2002
We describe several scenarios of basic femtosecond machining and materials processing that should... more We describe several scenarios of basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high through-put deep hole drilling in polymers and glasses in ambient air, and precision high speed micron-scale surface modification of materials.
Proceedings of SPIE - The International Society for Optical Engineering, 2004
Ti:Sapphire lasers remain the most widely used utlrafast laser. However, precise optical alignmen... more Ti:Sapphire lasers remain the most widely used utlrafast laser. However, precise optical alignment and environmental control are necessary for continuous, long-term stable operatoin of the laser. IMRA's FCPA laser is an air-cooled, Yb fiber-based ultrafast laser designed to operate in an industrial environment and provide a stable, high-quality laser beam. In this work, the micromachining performance of the FCPA laser
Proceedings of SPIE - The International Society for Optical Engineering, 2005
We report on the light transport phenomena in linear chains composed of several tens of touching ... more We report on the light transport phenomena in linear chains composed of several tens of touching spherical microcavities. A new optical mode type, namely nanojet-induced modes (NIMs) is observed. These modes result from the optical coupling of microspheres acting as a series of micro-lenses, which periodically focus propagating wave into photonic nanojets. Theoretically, formation of periodic nanojets has been predicted in Z. Chen et al., Opt. Lett. 31, 389 (2006). The chains were produced by means of the self-assembly directed by micro-flows of water suspension of polystyrene microspheres. The mean size of spheres was varied in the 2-10 micron range. To couple light to NIMs we used built-in emission sources formed by several locally excited dye-doped microcavities from the same chain. Conversion of modes emitted by the light source into the NIMs results in losses of several dB per sphere in the vicinity (first few tens of spheres) of such sources. At longer distances we found an attenuation rate as small as 0.5 dB per sphere that reveals low intrinsic propagation loss for NIMs. The NIMs have potential applications for coupling and guiding of light in compact arrays of spherical cavities with extremely high quality (Q) whispering gallery modes.
Proceedings of SPIE - The International Society for Optical Engineering, 2005
Direct waveguide writing with femtosecond lasers can be divided into two general categories based... more Direct waveguide writing with femtosecond lasers can be divided into two general categories based upon the type of lasers used: amplified systems that emit high pulse energy (>2 μJ) at low repetition rates (<250 kHz), and oscillators that produce low energy (<200 nJ) at high ...
Proceedings of SPIE - The International Society for Optical Engineering, 2006
High average power single-mode fiber lasers have attracted significant attention as alternatives ... more High average power single-mode fiber lasers have attracted significant attention as alternatives to conventional solidstate lasers owing to their relative high brightness, compactness and robustness. Likewise the turn-key operation of industrially qualified ultrafast fiber oscillators is well established. In recent years the convergence of reliable ultrafast fiber oscillators, high brightness pump diodes and high power fiber amplifiers has enabled ultrafast
Proceedings of SPIE - The International Society for Optical Engineering, 2006
Fiber lasers offer an excellent technology base for production of an industrial-quality tool for ... more Fiber lasers offer an excellent technology base for production of an industrial-quality tool for precision microfabrication, answering the need to expand the capabilities of laser material processing beyond traditional welding, cutting, and other industrial processes. IMRA&#39;s FCPA muJewelTM femtosecond fiber laser has been developed to address the particular need for direct-write lasers for creation of clean and high-quality micron and
Laser Technology for Defense and Security V, 2009
We have designed and developed a grating based thulium (Tm) doped fiber laser with ~150 nm tuning... more We have designed and developed a grating based thulium (Tm) doped fiber laser with ~150 nm tuning range which is used as the master oscillator in a master oscillator power amplifier (MOPA) thulium fiber laser system. Due to thermal instability in the grating used for tuning, the MO could produce a power up to 4.5 W, beyond which the oscillator
Advanced Solid-State Lasers, 2002
ABSTRACT © 2002 Optical Society of America
Summaries of Papers Presented at the Lasers and Electro-Optics. CLEO '02. Technical Diges, 2002
... Mysyrow-Miura, J. Qiu, K. Hirao, Anomalous icz, Writing of permanent birefringent mi-anisot... more ... Mysyrow-Miura, J. Qiu, K. Hirao, Anomalous icz, Writing of permanent birefringent mi-anisotropic light scattering in Ge-doped sil-crolayers in ... Fabrication of Waveguides and Gratings in Chalcogenide Thin Films A. Zoubir, L. Shah, MC Richardson, C. Rivero, C. Lopez and KA ...
Guided mode resonance filters produced a stable spectrally narrow Thulium fiber laser, at ~1985 n... more Guided mode resonance filters produced a stable spectrally narrow Thulium fiber laser, at ~1985 nm. Laser spectral linewidths of 10-30 pm with a slope efficiency of ~35% were demonstrated. Spectral reflectivity was explored and showed 0.4-1.0 nm FWHM.
Journal of Laser Micro/Nanoengineering, 2006
The need for improved precision in a wide variety of micromachining applications has driven scien... more The need for improved precision in a wide variety of micromachining applications has driven scientific interest in ultrashort pulse lasers. Despite numerous demonstrations of reduced heat effect and improved processing quality, the utility of such lasers has been limited by the heavy demands placed upon laser performance. In addition to high contrast laser pulses with minimal pulse-to-pulse fluctuation, an ultrashort pulse laser must provide near diffraction-limited beam quality and robust long-term laser operation with high repetition rate for high processing speeds. We report here on a research prototype, high power femtosecond fiber chirped pulse amplification system. The system produces compressed pulses with energies >50 µJ at >15 W with M 2 <1.4. The use of cubicon pulses, i.e. stretched pulses with cubical spectral and temporal shape, enables pulse compression to <500 fs with >1000:1 temporal contrast despite significant self-phase modulation during amplification corresponding to a nonlinear phase delay of ~6π. As a demonstration of high speed femtosecond micromachining, we drill and cut 0.5-mm thick metal, semiconductor and dielectric targets.
Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class... more Progress in the growth of the rare earth calcium oxyborate crystals has now generated a new class of laser materials that can be used as both a laser host and a nonlinear frequency converter. Laser action and self-frequency doubling (SFD) has been observed with both 10% and 20% Yb3+-doped YCOB crystals. Laser operation was obtained in a hemispherical linear cavity,
Development of the oxyborate Nd3+:YCOB has brought about the realization of single crystal elemen... more Development of the oxyborate Nd3+:YCOB has brought about the realization of single crystal elements under diode pumped operation for compact simple, solid state lasers producing visible laser emission. Efficient laser action and self-frequency doubling (SFD) has been obtained for both Ti:Sapphire and diode pumped operations. Comparable results were obtained for a hemispherical linear cavity with a 2% output coupler for
Abstract: We present an Yb:YAG thin-disk oscillator providing a tunable linewidth of 50-pm via VB... more Abstract: We present an Yb:YAG thin-disk oscillator providing a tunable linewidth of 50-pm via VBG-based feedback. Output powers of up to 2 W have been recorded while maintaining an excellent spatial profile. © 2011 Optical Society of America OCIS codes: (140.0140) ...
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
Abstract A system for multi-kilometer atmospheric propagation experiments including a master osci... more Abstract A system for multi-kilometer atmospheric propagation experiments including a master oscillator with~ 108 nm tunability and a power amplifier tested as an oscillator with~ 58% slope efficiency and stable 200 W output power is discussed.
The generation of stretched 20 pJ pulses with 200 kW peak power is demonstrated in an in-line Yb ... more The generation of stretched 20 pJ pulses with 200 kW peak power is demonstrated in an in-line Yb fiber chirped pulse amplification system at a repetition rate of 50 kHz. The pulses are compressible down to 400 fs using nonlinear cubical dispersion compensation.
Applied Physics A-materials Science & Processing, 2003
We describe several approaches to basic femtosecond machining and materials processing that shoul... more We describe several approaches to basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high-throughput deep hole drilling in glasses in ambient air, and precision highspeed micron-scale surface modification of composite materials and chalcogenide glasses. Ablation of soda-lime silicate glass and PbO lead-silicate is studied under three different sets of exposure conditions, for which both the wavelength and pulse duration are varied. Ablation rates are measured below and above the air ionization threshold. The differences observed are explained in terms of self-channeling in the ablated hole. Fabrication of practical devices such as waveguides and gratings is demonstrated in chalcogenide glass.
We describe several scenarios of basic femtosecond machining and materials processing that should... more We describe several scenarios of basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high through-put deep hole drilling in polymers and glasses in ambient air, and precision high speed micron-scale surface modification of materials.
Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XIII, 2014
ABSTRACT We present the characterization of thermal distortion induced in bulk and orientation-pa... more ABSTRACT We present the characterization of thermal distortion induced in bulk and orientation-patterned GaAs samples by a 100 W narrow linewidth, linearly polarized CW Tm:fiber laser focused to ~150 μm diameter. For a 500-μm thick bulk GaAs sample, the induced thermal distortion is measured using a probe laser beam at 1080 nm and a Shack-Hartmann wavefront sensor (SHWS). We also compare the power dependent induced divergence for 500-μm thick bulk GaAs and 10-mm thick orientation-partnered GaAs (OP-GaAs) samples as they are translated axially through the focus of a 2-μm wavelength Tm:fiber laser beam.
Proceedings of SPIE - The International Society for Optical Engineering, 2002
We describe several scenarios of basic femtosecond machining and materials processing that should... more We describe several scenarios of basic femtosecond machining and materials processing that should lead to practical applications. Included are results on high through-put deep hole drilling in polymers and glasses in ambient air, and precision high speed micron-scale surface modification of materials.
Proceedings of SPIE - The International Society for Optical Engineering, 2004
Ti:Sapphire lasers remain the most widely used utlrafast laser. However, precise optical alignmen... more Ti:Sapphire lasers remain the most widely used utlrafast laser. However, precise optical alignment and environmental control are necessary for continuous, long-term stable operatoin of the laser. IMRA's FCPA laser is an air-cooled, Yb fiber-based ultrafast laser designed to operate in an industrial environment and provide a stable, high-quality laser beam. In this work, the micromachining performance of the FCPA laser
Proceedings of SPIE - The International Society for Optical Engineering, 2005
We report on the light transport phenomena in linear chains composed of several tens of touching ... more We report on the light transport phenomena in linear chains composed of several tens of touching spherical microcavities. A new optical mode type, namely nanojet-induced modes (NIMs) is observed. These modes result from the optical coupling of microspheres acting as a series of micro-lenses, which periodically focus propagating wave into photonic nanojets. Theoretically, formation of periodic nanojets has been predicted in Z. Chen et al., Opt. Lett. 31, 389 (2006). The chains were produced by means of the self-assembly directed by micro-flows of water suspension of polystyrene microspheres. The mean size of spheres was varied in the 2-10 micron range. To couple light to NIMs we used built-in emission sources formed by several locally excited dye-doped microcavities from the same chain. Conversion of modes emitted by the light source into the NIMs results in losses of several dB per sphere in the vicinity (first few tens of spheres) of such sources. At longer distances we found an attenuation rate as small as 0.5 dB per sphere that reveals low intrinsic propagation loss for NIMs. The NIMs have potential applications for coupling and guiding of light in compact arrays of spherical cavities with extremely high quality (Q) whispering gallery modes.
Proceedings of SPIE - The International Society for Optical Engineering, 2005
Direct waveguide writing with femtosecond lasers can be divided into two general categories based... more Direct waveguide writing with femtosecond lasers can be divided into two general categories based upon the type of lasers used: amplified systems that emit high pulse energy (>2 μJ) at low repetition rates (<250 kHz), and oscillators that produce low energy (<200 nJ) at high ...
Proceedings of SPIE - The International Society for Optical Engineering, 2006
High average power single-mode fiber lasers have attracted significant attention as alternatives ... more High average power single-mode fiber lasers have attracted significant attention as alternatives to conventional solidstate lasers owing to their relative high brightness, compactness and robustness. Likewise the turn-key operation of industrially qualified ultrafast fiber oscillators is well established. In recent years the convergence of reliable ultrafast fiber oscillators, high brightness pump diodes and high power fiber amplifiers has enabled ultrafast
Proceedings of SPIE - The International Society for Optical Engineering, 2006
Fiber lasers offer an excellent technology base for production of an industrial-quality tool for ... more Fiber lasers offer an excellent technology base for production of an industrial-quality tool for precision microfabrication, answering the need to expand the capabilities of laser material processing beyond traditional welding, cutting, and other industrial processes. IMRA&#39;s FCPA muJewelTM femtosecond fiber laser has been developed to address the particular need for direct-write lasers for creation of clean and high-quality micron and