Continuous-wave, intracavity optical parametric oscillators: an analysis of power characteristics

Received: 29 December 1997/Revised version: 6 February 1998     

A frequency-doubled pulsed chemical oxygen-iodine laser

The intracavity second-harmonic generation of pulsed chemical oxygen-iodine laser radiation was investigated. A pulsed chemical oxygen-iodine laser with a maximum output energy of 6.14 mJ was used. The second-harmonic output of 0.5 mJ was demonstrated using a lithium iodate crystal. The conversion efficiency of 8% was limited by intracavity losses. Numerical simulation predicts that a conversion efficiency of 75% can be obtained with 1% intracavity losses.     

Efficient generation of tunable VUV laser radiation below 205 nm by SFM in BBO

Design and performance characteristics of a tunable dye laser system for sum frequency mixing (SFM) in a BBO crystal are presented. The system is composed of two tunable pulsed dye lasers pumped synchronously by the second harmonic of a commercial Nd:YAG laser. The radiation produced by the first dye laser is frequency doubled by second-harmonic generation (SHG) in KDP and subsequently mixed by SFM in BBO with the light of the second dye laser. The interest was focussed on generation of tunable laser radiation below 205 nm with high output power and long-time wavelength stability. High conversion efficiencies enable output energies of 100 J (20 kW) at 196 nm using only moderate Nd:YAG pump energies of 67 mJ. Altogether, a laser system with very good specifications for analytical application in the near VUV spectral region is reported.     

Short pulse, high peak power, diode pumped, passively Q-switched 946 nm Nd:YAG laser

We report on generation of 946 nm laser pulses of a few nanosecond duration and up to 3.7 kW peak power from a compact diode-pumped passively Q-switched Nd:YAG laser. This power is 2.5 times as much as what previously has been obtained from this type of a laser. The short pulses with the record high peak power may be particularly attractive for laser range finding type applications.     

Generation of 17-TW 23-fs Pulses with a Two-Stage Ti：Sapphire Amplifier at Repetition Rate 10 Hz

We have developed a two-stage Ti：sapphire amplifier system which can produce 17- TW/23-fs pulses at a repetition rate 10Hz. A birefringent plate is used in the regenerative amplifier to alleviate gain narrowing, while an all- reflective cylindrical-mirror-based pulse stretcher and an acousto-optic programmable dispersive filter （AOPDF） are used to compensate for the higher order dispersion of the system.     

Feedback-controlled optimization of amplified femtosecond laser pulses

Received: 17 December 1998     

A frequency doubled chemical oxygen iodine laser

The output of a chemical oxygen iodine laser (=1.315 m) has been frequency doubled at an overall conversion efficiency of 1%. A lithium iodate (LiIO₃) crystal was used in an intracavity doubling scheme. This represents the first time visible laser light has been obtained, solely from a chemical source.To whom the correspondence should be addressed.     

Subnanosecond pulse measurements of 10.6 μm radiation with tellurium

Subnanosecond infrared pulses have been measured by noncollinear secondharmonic generation in tellurium. The method is very practical because due to the high refractive index the fine tuning of the phase matching is easily obtained by rotating the crystal around the optic axis.     

Generation of coherent ultraviolet radiation in the 330 nm region by multiphoton excitation of sodium vapor

We report the observation of coherent uv emission at 330.2±0.5 nm when sodium vapor in a heatpipe is irradiated with a pulsed visible dye laser with output wavelength in the 570–595 nm region. It is found that intense uv emission can be produced from Na atoms as well as from Na₂ molecules. The excitation functions and their dependence on vapor density and laser power density are presented and the mechanisms for producing the emission are discussed.On leave from the Department of Physics, Fujian Normal University, Fuzhou, Fujian, People's Republic of China     

Single picosecond UV pulse generation by mode-locking of an excimer laser-pumped dye laser

A single picosecond ultraviolet pulse has been generated based on mode-locking of a dye laser pumped by a long pulse XeCl laser to serve as the input source for a high-power ps KrF laser system. A short-pulse uv dye laser (BBQ) pumped by an additional XeCl laser was used to selectively amplify a single pulse from a mode-locked pulse train with the pulse separation of 3.2 ns. The amplified single pulse was frequency-doubled to 248 nm with the pulse duration of 20 ps.     

Additive pulse mode-locked Nd: YAG laser

Additive pulse mode locking applied to lamppumped Nd: YAG lasers results in an attractive source of picosecond pulses at 1.06 m or 1.32 m with average powers at the Watt level. We provide detailed information on construction and operation and give data on performance. A modified active stabilization scheme allows not only improved stability of operation but also insight into the dynamics of pulse formation.     

Tuning ranges of KrF and ArF excimer laser amplifiers and of associated vacuum ultraviolet anti-Stokes Raman lines

Measurements of tuning ranges for narrow-bandwidth ( ) radiation amplified in KrF and ArF laser amplifiers are reported. Generation of high-order anti-Stokes Raman lines in H₂ down to 116 nm is described as well as measurements of the corresponding tuning ranges. Generation of rotational side-bands opens the possibility to tune most of the vacuum-ultraviolet (vuv) lines over intervals in excess of 1400 cm^–1. Absolute values of the power measured for the various vuv lines are communicated.     

SOA-based actively mode-locked fiber ring laser by forward injecting an external pulse train

An actively mode-locked fiber ring laser based on cross-gain modulation (XGM) in a semiconductor optical amplifier (SOA) is demonstrated to operate stably with a simple configuration. By forward injecting an easily-generated external pulse train, the mode-locked fiber laser can generate an optical-pulse sequence with pulsewidth about 6 ps and average output power about 7.9 mW. The output pulses show an ultra-low RMS jitter about 70.7 fs measured by a RF spectrum analyzer. The use of the proposed forward-injection configuration can realize the repetition-rate tunability from 1 to 15 GHz for the generated optical-pulse sequences. By employing a wavelength-tunable optical band-pass filter in the laser cavity, the operation wavelength of the designed SOA-based actively mode-locked fiber laser can be tuned continuously in a wide span between 1528 and 1565 nm. The parameters of external-injection optical pulses are studied experimentally to optimize the mode-locked fiber laser.     

Generation of high-quality 10-femtosecond laser pulses with intracavity spatial and spectral control

Spatial and spectral control, using an intracavity capillary and a slit, is applied to improve the output pulse quality of a Ti:sapphire laser. Satellite-free 10-fs optical pulses with a smooth spectral and spatial profile have been generated. Employing a root-mean-square formalism for pulse characterization, spatial, spectral and temporal intensity distributions are analyzed for laser pulses with a duration as short as three to four optical cycles. Received: 11 June 2001 / Published online: 18 July 2001     

Mid-IR Dual-Wavelength Difference Frequency Generation Using Fiber Lasers as Pump and Signal Light Sources

A continuous-wave mid-IR difference frequency laser source, which respectively uses an ytterbium-doped fiber laser as the pump source and a multiwavelength erbium-doped fiber laser cascaded with an erbium-doped fiber amplifier as the signal source, is demonstrated. Our experimental results show that two stable mid-IR radiation lines with a spacing of about 5.4nm may be simultaneously emitted by a suitable setting the pump and signal polarization orientations. The number of the mid-IR radiation lines is limited by the quasi-phase-matching acceptance bandwidth. By changing the PPMgLN temperature the two mid-IR radiation lines may be synchronously tuned in the mid-IR range between 3295 and 3356.3nm.     

Amplification of kW peak power femtosecond pulses in single quantum well InGaAs tapered amplifiers

The amplification of ps and fs pulses with peak powers of up to 4.5 kW has been investigated in a single quantum well InGaAs tapered amplifier. The pulses with durations of 100 fs or 2 ps were generated by a modelocked titanium-sapphire laser. The amplified pulses indicate strong gain saturation and carrier generation due to photon absorption in the laser active region which causes a temporal broadening of the amplified pulses as well as modifications of the optical spectrum. The gain recovery time was measured by a pump-probe experiment. The experimental results are analyzed with respect to the sub-ps gain dynamics which is described by a relaxation time approximation.     

Excimer laser processing of embedded fibers

Novel aspects of the excimer laser etching of nanostructures in embedded optical fibers are discussed. Emphasis is put on the etching of a specified hole geometry and on excellent surface quality of the hole walls.On leave from: Institute of Quantum Electronics, ETH, CH-8093 Zürich, Switzerland     

Periodic pulse solutions of a laser consisting of a pair of amplifiers mode locked by a fast saturable absorber

We present periodic solutions, which are described in terms of Jacobian elliptic functions, for the steady state pulses from a laser system consisting of a pair of amplifiers of unequal relaxation time mode locked by a “fast” saturable absorber. The pulsewidth and the average power in the pulse are expressed interms of the system parameters through two different approaches, where detailed plots are given for one of the approaches. Summary of the characters to be possessed by the amplifier pair to ensure the reliable production of shortest possible pulses is given.     

The self-injected XeCl excimer laser

We present experimental and modelling results of the first self-injected excimer laser. The intracavity losses of a XeCl oscillator are properly modulated by a Pockels cell allowing generation, amplification and extraction of short laser pulses with selectable duration in the range of 1–12 ns, tailored temporal profile and peak power increment up to a factor of three. Longer output laser pulses, up to 100 ns, can be obtained by slicing the intracavity laser radiation without peak power increment. Laser output peak powers in excess of 2 MW have been obtained, with remarkable reproducibility characteristics.ENEA fellow     

14-fs high temporal quality injector for ultra-high intensity laser

We present a chirped pulse amplification (CPA) Ti:Sa laser generating sub-15 fs pulses with expected high temporal quality. Gain-narrowing in the pre-amplifier is balanced by a variable spectral reflectivity mirror and by a fine adaptation of the saturation conditions. A crossed polarized wave generation (XPW) filter is introduced to enhance the contrast, reduce the pulse duration and improve the spectral quality. The pulses are generated at 10 Hz repetition rate, with pulse energy of 110 μJ and very clean Gaussian spectrum. The temporal contrast is evaluated by a measurement before the XPW filter and calculations of the enhancement by the filter. The potential temporal incoherent contrast is 10¹² and the coherent contrast 10¹⁰. The performance of the system makes it suitable as an injector for petawatt lasers operating in the double-CPA scheme.