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The amplification of light by a single excited molecule in free space is demonstrated in this paper. The extinction effect is the result of a destructive interference between the incident laser beam and the coherently scattered light from the molecule in the ground state. Thus, inversion of the population should lead to a phase shift of the scattered light and amplification of the laser light.
We report helicoidal long-period grating by twisting photonic crystal fiber under CO2 laser irradiation and investigated its novel characteristics. The fabricated PCF-LPG endows unique resonance tuning capability with low polarization-dependent loss and thermal shift.
We review the basic principles of the femtosecond laser direct writing approach. This technology opens the possibility to specifically tune the light evolution in the linear as well as in the nonlinear regime.
We realized a continuous-wave terahertz spectrometer based on optical heterodyning of two near-infrared distributed-feedback diode lasers. Using active frequency stabilization we achieve 1 MHz resolution and a signal-to-noise ratio up to 80 dB.
We demonstrated an array of distributed feedback quantum cascade lasers covering a spectral range of 220 cm-1. The variability in threshold current and slope efficiency is explained in terms of the position of the laser end facets.
Wavelength modulation waveforms were studied in tunable diode laser photoacoustic spectroscopy by way of simulations and experiments. The modulation waveforms were sinusoidal, triangular, shaped, and quasi-square waves. The quasi-square waveform gave the largest signal-to-noise ratio.
We describe the use of a semiconductor optical amplifier as an intra cavity, continuous phase tuning element in an optoelectronic oscillator. A tuning range larger than 3 MHz is demonstrated in a 10 GHz oscillator.
The production of highly energetic beams of both electrons and ions is a major part of the experimental programme at the Central Laser Facility (CLF), STFC Rutherford Appleton Laboratory. Every year sees a significant number of experiments done in both areas. This has been complemented by theoretical studies that have been carried out at the CLF and UK universities. In a recent consultation on plans...
A phase-locked 110-GHz continuously-tunable optical-single-frequency generator is developed based on a phase-stabilized fiber-based comb. Stability of the optical frequencies at 1s are 3.0 and 31times10-12 at scanning speeds of 0.17 and 1 GHz/s, respectively.
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.
A 65-nm quasi-continuous tuning range is reported for a 3.5-mm-wide optically pumped type-II chirped-grating distributed-feedback laser at 3.2 mum. Methane absorption spectra demonstrate the utility of this source for atmospheric-pressure molecular spectroscopy.
Coupling a microdisk based laser to an external passive cavity can be used to strengthen mode selectivity and get a single, unidirectional and tunable output waveguide.
Using polarization spectroscopy to control the shape of the diode current ramp while tuning an external cavity diode laser we achieved mode-hop free tuning of up to 105 GHz with an uncoated, off-the-shelf laser diode.
A Winston cone is used to concentrate the emitted radiation of a mid-infrared LED onto a small spot on the side of one prong of a quartz tuning fork acting as a detector. The Winston cone is used as an absorption cell as well, thus providing a very compact and cost efficient mid-infrared sensing system.
Tunable narrow-linewidth operation of an Yb-doped fiber amplified-spontaneous-emission (ASE) source is reported. The source yielded 135 mW output at 1040 nm and could be tuned from 1034 nm to 1084 nm. The prospects for improvement in performance are considered.
Tunable edge emitting microlaser was realized with a line defect waveguide, in which the radii of holes adjacent to the defect was varied gradually. A tunable range of 17 nm was obtained experimentally.
Mid-infrared beam shaping is demonstrated by using grating coupled surface emitting quantum cascade ring lasers. The devices allow for far-field tuning, ranging from highly symmetric spot-to ring-shaped beam patterns, depending on the grating period.
We present two new depth resolved holographic imaging concepts with spectrally tunable diode lasers. Variable depth resolution is achieved by changing the tuning width and a concept for single-shot recording of a 3D-image is introduced.
A novel Er:fiber/Ti:sapphire hybrid laser generates phase-locked few-cycle terahertz transients tunable from 1 to 107 THz and electric fields of up to 108 MV/cm. 8-fs pulses from the fiber laser serve as electro-optic probe.
We demonstrate a new technique for fine tuning of optical delays using cascaded acousto-optic modulators. A 256-ns delay with <0.5-ps resolution is shown for 40-Gb/s RZ-OOK with no system penalty.
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