Experiment and modeling of a diode-pumped 1.3 μm Nd:YVO<Subscript>4</Subscript> laser passively Q-switched with PbS-doped glass

A diode-pumped 1.34 m Nd:YVO₄ laser passively Q-switched with PbS quantum dots doped glass is presented. An average output power of 24 mW with a Q-switching efficiency of 13% and a Q-switched pulse width of 15 ns was obtained. A four level spectroscopic model of a PbS quantum dots doped glass saturable absorber is applied to numerically simulate passively Q-switched Nd:YVO₄ laser operation. It has been shown that for the simulation of passive Q-switching of 1.3 m Nd:YVO₄ lasers with PbS doped glasses as the saturable absorbers, it is necessary to take into account intensity dependence of bleaching relaxation times. PACS 42.60.Gd; 42.55.Xi; 42.70.Hj     

Self-starting five optical cycle pulse generation in Cr<Superscript>4+</Superscript>:YAG laser

We report stable self-starting near-transform-limited 26-fs pulses at 250-mW output power from a Kerr-lens mode-locked (KLM) Cr⁴⁺:YAG laser using chirped mirrors in combination with prisms. The highest output power achieved in KLM regime was 600 mW at 55-fs pulse duration. The experimental results agree well with the results of theoretical analysis with respect to KLM self-starting ability and stability against continuous-wave and multi-pulse operation. Parameter ranges for stable transform-limited KLM pulses as well as the shortest achievable pulse durations are established. Using an InGaAs-InP semiconductor saturable absorber mirror we could obtain self-starting 57-fs pulses at the average output power of 200 mW. Two-photon absorption was found to be the main mechanism favoring the multiple-pulse operation. Received: 2 May 2002 / Revised version: 16 July 2002 / Published online: 8 January 2003 RID="*" ID="*"Corresponding author. Fax: +43-1/58801-38799, E-mail: sorokina@tuwien.ac.at     

Suppression of gain narrowing in multi-TW lasers with negatively and positively chirped pulse amplification

A laser scheme implementing a combination of negatively and positively chirped pulse amplification (NPCPA) is demonstrated. This method of amplification suppresses spectral narrowing typically appearing in chirped pulse amplification (CPA) lasers thus supporting pulse spectrum much broader than a conventional CPA. With a NPCPA Ti:Sapphire laser we have achieved laser pulses of 50 nm spectral width and 150 mJ energy without any additional spectral correction. The scheme appears as an easy and reliable solution to preserve spectral bandwidth in Ti:Sapphire lasers, especially at high power levels up to the Petawatt regime. PACS 42.60 By, Lh; 42.65 Re     

Use of α-2-cyanoethyl tert-butoxycarbonylaspartate as an intermediate for synthesis of β-esters

The use of -2-cyanoethyl Boc-aspartate is proposed for the first time for the synthesis of -esters of Boc-aspartic acid. The -2-cyanoethyl protective group is selectively split out by strong organic bases under hydrolytic conditions without the -ester bond being affected. Using the -2-cyanoethyl derivative, -cyclohexyl, -benzyl, and -tert-butyl Boc-aspartates have been synthesized in good yields.All-Union Scientific-Research Institute of Molecular Biology. Vektor Scientific-Industrial Association. Ministry of the Medical and Biochemical Industries, Koltsovo, Novosibirsk Province. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 241–245, March–April, 1990.     

Derivation of classical Markovian kinetic equations via generating functional technique

An exact Markovian kinetic equation for a classical system of particles interacting via pair forces is derived by means of Bogoljubov's Generating Functional method. A nondiverging collision integral is obtained for Coulomb plasmas, which takes into account the screening effects and the energy and momentum transfer between two colliding particles and their surroundings.