P. Heinz

Intense subpicosecond pulses tunable between 4 μm and 20 μm generated by an all-solid-state laser system

Abstract The generation of widely tunable ultrashort mid-infrared pulses with intensities sufficient for a substantial excitation of infrared states is discussed. Single pulses of 1 ps duration and an energy of 7 mJ from an APM mode-locked Nd:glass laser with regenerative amplifier (repetition rate 4 Hz) serve as pump pulses. A three-path optical parametric generator pumped by the second harmonic of the Nd-laser produces tunable near infrared pulses. Subsequent down conversion in GaSe provides pulses of 0.7 ps duration tunable between 4 μm and 20 μm. Energies up to 25 μJ are measured.

Stable generation of subpicosecond pulses by feedback-controlled mode locking of a Nd:glass laser

A high-performance subpicosecond Nd:glass laser with feedback-controlled mode locking is described. Depending on operation conditions, the laser oscillator generates single pulses of 0.80-psec duration and 10-μJ energy or microsecond trains of approximately 400 pulses with 1.3-psec duration and 0.8-mJ total energy. Stable performance, a repetition rate of 6–10 Hz, and a peak-to-background intensity ratio of >5 × 105 are reported.

Feedback-controlled mode-locking operation of Nd-doped crystal lasers

Feedback-controlled mode locking (FCM) of Nd:YAG-, YAP-, and YLF-laser oscillators with superior pulse properties is demonstrated. Microsecond trains of ultrashort laser pulses are generated with durations of 11 psec (YAG), 9.8 psec (YAP), and 6.7 psec (YLF), respectively, governed by the fluorescence linewidths. Inserting an antiresonantly tuned etalon in the cavity yields stable operation with even shorter pulses of 6.4, 5.9, and 4.7 psec, respectively, and a reproducibility of ±5%.

Feedback control of an actively-passively mode-locked Nd:Glass laser

Improved performance of a pulsed solid-state laser by electrooptic amplitude control is reported. A sequence of ≃200 pulses is reproducibly generated with 10 Hz repetition rate, 3 ps duration and 300 μJ total energy. The microsecond pulse trains are particularly interesting as a pump source of pulsed fs dye lasers.

Additive-pulse modelocking of non-cw neodymium lasers

Abstract Passive modelocking of several flash-lamp pumped neodymium lasers with electro-optic amplitude stabilization is demonstrated using a nonlinear Michelson interferometer. Improved performance is reported for the GSGG- YLF- and glass-laser as compared to the nonlinear absorber, with shorter pulse durations and smaller amplitude fluctuations, e.g. 5 μJ pulses for 460 ± 20 fs for Nd:glass. Evidence is obtained for multi-selfstability of the pulse energy.

Electro-optic gain control and cavity dumping of a Nd: Glass laser with active-passive mode-locking

Abstract Improved operation of a 10 Hz, hybrid-modelocked glass laser is reported. Generating transient cavity losses during the nonlinear regime of pulse formation yields shorter pulses of 2.5 ps duration and improved reproducibility. The background level of satellite pulses is simultaneously reduced by more than one order of magnitude.

Characterization of energy transfer for passively Q-switched laser ignition

Miniaturized passively Q-switched Nd:YAG/Cr(4+):YAG lasers are promising candidates as spark sources for sophisticated laser ignition. The influence of the complex spatial-temporal pulse profile of such lasers on the process of plasma breakdown and on the energy transfer is studied. The developed measurement technique is applied to an open ignition system as well as to prototypes of laser spark plugs. A detected temporal breakdown delay causes an advantageous separation of plasma building phase from energy transfer. In case of fast rising laser pulses, an advantageous reduction of the plasma breakdown delay occurs instead.

Pulsed diode-pumped additive-pulse mode-locked high-peak-power Nd:YLF laser

Intense ultrashort pulses are generated in an additive-pulse mode-locked, amplitude-feedback-controlled Nd:YLF laser pumped by quasi-cw laser diodes with a 30-Hz repetition rate. Pulse trains are produced that consist of approximately 600 single pulses of 2.1-ps duration and less, similar1-microJ energy. The peak intensity is less, similar0.5 MW, and a stability corresponding to a standard deviation of ~1.3% is measured. The optical efficiency of this all-solid-state mode-locked laser is determined to be ~1%.

Feedback-controlled mode-locking operation of a Nd:YLF laser at 1.047 μm

Abstract Feedback-controlled mode locking (FCM) of a Nd:YLF laser at 1.047 μm is demonstrated. The larger stimulated emission cross section of the π-polarized (λ=1.047 μm) transition compared to the cross section of the σ-polarized (λ=1.053 μm) transition leads to a lower pump energy threshold. Inserting an anti-resonantly tuned etalon in the cavity yields stable operation with short bandwidth-limited pulses of less than 3 ps at a repetition rate of 70 Hz.

Picosecond Nd:YLF laser-multipass amplifier source pumped by pulsed diodes for the operation of powrful OPOs

Abstract Picosecond pulse trains from a quasi cw Nd:YLF oscillator are amplified by a multipass system pumped by a pulsed 100 W peak power laser diode. Gain factors in the order of 100 are achieved with input pulses of 100 nJ energy and 2 ps duration. The high power of the amplified pulse trains allows the operation of a quasi-cw synchronously pumped KTP optical parametric oscillator (OPO) at high output coupling. Pumping by the second harmonic provides OPO pulses of 2.1 ps duration in trains consisting of 25 pulses with a noteworthy flat top of the envelope. The conversion efficiency of 13% corresponds to a total energy of 50 μJ in the trains. The parameters promise wide applications of the system in ultrafast spectroscopy.