Optimal design for wavelength conversion with a configuration of walk-off compensation in free space in the nanosecond pulsed regime.

On the basis of standard wavelength conversion by the use of angular phase matching of nonlinear optical crystals arranged in free space, applicable to a wide range of wavelengths and laser intensities, we both numerically and experimentally present an optimal design for achieving near-full energy conversion while maintaining good TEM mode property of fundamental laser radiation in the nanosecond regime.

10 W injection-locked single-frequency continuous-wave titanium:sapphire laser.

High-power tunable lasers with good longitudinal and transverse modes are fundamental tools for exploring quantum physics. Here we report a high-power continuous-wave injection-locked titanium:sapphire laser with a low-loss cavity configuration, where only a laser crystal was installed in the laser cavity. Although the transverse mode was affected by a thermal lens formed in the laser crystal, the focal length of the thermal lens could be shifted via the temperature of the laser crystal holder or the pump power.

Dual-frequency injection-locked continuous-wave near-infrared laser.

We report a dual-frequency injection-locked continuous-wave near-infrared laser. The entire system consists of a Ti:sapphire ring laser as a power oscillator, two independent diode lasers employed as seed lasers, and a master cavity providing a frequency reference. Stable dual-frequency injection-locked oscillation is achieved with a maximum output power of 2.

Generation of five phase-locked harmonics by implementing a divide-by-three optical frequency divider.

We report the generation of five phase-locked harmonics, f₁:2403  nm, f₂:1201  nm, f₃:801  nm, f₄:600  nm, and f₅:480  nm with an exact frequency ratio of 1:2:3:4:5 by implementing a divide-by-three optical frequency divider in the high harmonic generation process. All five harmonics are generated coaxially with high phase coherence in time and space, which are applicable for various practical uses.

Freely designable optical frequency conversion in Raman-resonant four-wave-mixing process.

Nonlinear optical processes are governed by the relative-phase relationships among the relevant electromagnetic fields in these processes. In this Report, we describe the physics of arbitrary manipulation of Raman-resonant four-wave-mixing process by artificial control of relative phases. As a typical example, we show freely designable optical-frequency conversions to extreme spectral regions, mid-infrared and vacuum-ultraviolet, with near-unity quantum efficiencies.

Dual-frequency injection-locked nanosecond pulsed laser with arbitrary combination of two oscillation frequencies.

We report a dual-frequency injection-locked nanosecond pulsed laser oscillating at an arbitrary combination of two frequencies over the broad gain range of a Ti:sapphire laser. This performance is achieved by employing two techniques. One involves introducing two different modulation frequencies to discriminate electronically the error signals, which are used for locking the two seed frequencies to the forced oscillator.

Femtosecond ultrashort pulse generation by addition of positive material dispersion.

We demonstrate femtosecond ultrashort pulse generation by adding further positive group velocity dispersion (GVD) to compensate for the presence of positive GVD. The idea is based on the integer temporal Talbot phenomenon. The broad Raman sidebands with a frequency spacing of 10.

Line-by-line control of 10-THz-frequency-spacing Raman sidebands.

We report line-by-line control of a coherent discrete spectrum (Raman sidebands) with a frequency spacing of 10.6 THz that is produced by an adiabatic Raman process. We show that the spectral phase of the Raman sidebands is finely controlled to the target (flat relative-spectral-phase).

Octave-spanning Raman comb with carrier envelope offset control.

We report that adiabatic manipulation of a Raman process allows us to produce an optical-frequency comb from single-frequency lasers. We realize an octave-spanning Raman comb with carrier-envelope-offset frequency control, by using dual-frequency laser radiation locked on a single laser cavity and simultaneously its second harmonic. It is shown that in both the temporal and spectral domains, locking the dual frequencies on a single laser cavity provides control of the carrier-envelope-offset frequency at integer multiples of the free spectral range of the laser cavity.

Spectral phase measurements for broad Raman sidebands by using spectral interferometry.

We report a method of spectral phase measurement for a femtosecond pulse train composed of a discrete Raman spectrum. The method is based on an idea of spectral interference. Making use of a small portion of two Raman pump laser radiations, we produce two sum-frequency spectra that spectrally interfere with each other.

Dual-frequency pulsed laser with an accurate gigahertz-beat note.

We report a novel nanosecond pulsed laser with a highly accurate gigahertz beat that is realized by injection locking to gigahertz sidebands generated from a single-frequency cw laser radiation using a Mach-Zehnder type intensity modulator. It is shown from both the spectrum of the pulsed sidebands and their coherent beat in the time domain that the frequency accuracy of an rf oscillator driving the intensity modulator is reflected in the injection-locked nanosecond pulse with an intense peak power of the megawatt class.

Dual-wavelength injection-locked pulsed laser with highly predictable performance.

The characteristics of a dual-wavelength injection-locked pulsed laser are systematically studied. A simple and effective model is proposed to quantitatively study this type of laser system. It is shown that the model precisely predicts the performance of such a system over a wide spectral region and a full dynamic range.

Dual-wavelength injection-locked pulsed laser.

An injection-locked pulsed Ti:sapphire laser oscillating at dual wavelengths is demonstrated for the first time to our knowledge. By use of two feedback loops, seeds of two independent master lasers are locked on specific longitudinal modes of a power oscillator, leading to a stable dual-wavelength oscillation over a long time scale. The two injection-locked pulsed outputs completely overlap in time, with spectral purities reaching a Fourier-transform limit.

Generation of a 10.6-THz ultrahigh-repetition-rate train by synthesizing phase-coherent Raman-sidebands.

A train of highly-stable, high-beam-quality ultrashort pulses is successfully produced by synthesizing phase-coherent rotational-Raman-sidebands in parahydrogen. The-intensity-waveform of this ultrashort-pulse-train is directly evaluated in time domain based on a sum-frequency-generation autocorrelation-technique. It is shown that a 10.

Chlamydia pneumoniae seropositivity predicts the risk of restenosis after percutaneous transluminal coronary angioplasty.

This study was done to evaluate whether anti-Chlamydia pneumoniae seropositivity can be a predictor of restenosis after coronary intervention. Recent studies indicate that latent infection with C. pneumoniae is associated with and could possibly cause atherosclerosis.