DD262946A1 - SAVERABLE ABSORBER FOR NITROGEN LASER - Google Patents

Abstract

The invention relates to a satellable absorber for nitrogen laser, in particular for TEA nitrogen laser for pulse shaping and pulse shortening. The invention is characterized in that the satellable absorber contains, as organic compound, an acceptor-substituted N, N-dialkylaminobenzene of the formula I where R1; R 2 is any alkyl radical, preferably a methyl group, and X is a cyano group (CN), an ester group (COOR with any alkyl radical R), but preferably an aldehyde group (CHO). For the N, N-dialkylaminobenzene, an organic solvent is provided which is transparent in the region around 337 nm, preferably ethanol, methanol, dimethyl sulfoxide, dioxane or tetrahydrofuran. Formula I

Description

Field of application of the invention

The invention relates to a saturable absorber for nitrogen laser, in particular for TEA nitrogen laser for pulse shaping and pulse shortening.

Characteristic of the known state of the art

TEA nitrogen lasers have a pulse width half width of about 500 ps as well as a shallow rise and fall of the pulse typical of super-sharks.

For many applications, such as for time-resolved spectroscopy and the generation of ultrashort dye laser pulses, further shortening of the nitrogen laser pulses is advantageous. In the same way, this also applies to the form of impulses.

For this purpose, two solutions are known from the literature. The first solution increases the gas pressure in the laser channel. With gas pressures of more than 4.times.10.sup.- ¹⁶ MPa, pulse widths of less than 100 ps can be achieved (Phys. Letters 28, 272, 272) Laser head with the associated elements must be arranged flameproof.

The second variant for pulse shortening is the use of saturable absorbers. In this case, for example, a corresponding dye solution is arranged in the beam path of the laser. For nitrogen lasers, only the dyes p-bis (o-methylstyryl) -benzene and POPOP (1,4-di (2- (5-phenyloxazolyl)) - benzene have heretofore been used (J. Photochem., 14 [1980] 1; Proceedings ofthe4th, conference on luminescence, page 315, Szeged, 1982.) These dyes could be used to achieve pulse reductions of about 30%, which had the disadvantage of a very large attenuation of the momentum (93-96%).

Object of the invention

The aim of the invention is the pulse shortening or deformation of nitrogen laser pulses without great technical effort and only slight weakening of the laser pulses.

Explanation of the essence of the invention

The invention has for its object to provide saturable absorber based on dye with an absorption characteristic of 337 nm, which shorten the time as a passive optical switch the radiation of a nitrogen laser and deform and have a high cross section σ at the wavelength of the radiation of a nitrogen laser. The object is achieved according to the invention in that the saturable absorber contains as an organic compound an acceptor-substituted Ν, Ν-dialkylaminobenzene of the formula I,

O)-

Formula I ₍

where Ri; R _{2 is} any alkyl group, preferably a methyl group and X is a cyano group (-C = N), an ester group (-COOR with any alkyl radical R), but preferably an aldehyde group (-CHO). For the Ν, Ν-dialkylaminobenzene an organic solvent is provided which is transparent in the range of 337 nm, preferably ethanol, methanol, dimethyl sulfoxide, dioxane or tetrahydrofuran.

The absorption maximum of the compounds used according to the invention is dependent on the substituents R 1, R ₂ and X and the solvent used in the range of 320-380 nm, the absorption cross-section σ at 337 nm between

1 -. 2 1 (T ¹⁶ cm ² The main advantage of the present invention as a saturable absorber used acceptor-N _r N-Dialkylaminobenzene compared to the previously used for this purpose, organic compounds is that depending on the solvent used pulse reductions up to 30% The resulting losses are also solvent dependent and less than 30%.

embodiment

The invention is explained in more detail below with reference to two exemplary embodiments: No. 1: dimethylaminobenzaldehyde

CH.

No.2: Diethylaminobenzaldehyde

The parameters of the two selected compounds Nos. 1 and 2 are summarized in Table 1. In order to demonstrate their properties as saturable absorbers for nitrogen lasers, the solutions of Compound Nos. 1 and 2 were placed in an experimental setup. The laser used was a three-stage TEA nitrogen laser. The pulse half width was 500 ps and the pulse power about 50 okW.

The radiation of the laser was focused with a quartz lens on the cuvette (1 mm layer thickness) with the absorbing solution. The intensity of the excitation radiation could be varied between 10 MW / cm ² and 1 GW / cm ² . The laser radiation behind the cuvette was measured either with the PEM 512 energy meter or the TDS 200 streak camera system.

Table 1: Parameters of Compounds No. 1 and No. 2

No. Solvent A _max [nm] o (337nm) [cm ² ]

T "[%]

maximum pulse shortening

1 ethanol 340 1.1 1 dimethyl 341 1.1 2 ethanol 349 1.1

10ΙΟ "ΙΟ"

75 80 75

11 30 20

Claims (1)

Saturable dye-based absorber for nitrogen laser, characterized in that the saturable absorbing Q-switching element contains as an organic compound an acceptor-substituted Ν, Ν-dialkylaminobenzene of the formula I, Formula l _; wherein R ₁ ; R 2 is an arbitrary alkyl radical, preferably a methyl group, and X is a cyano group (-C ^ = N), an ester group (-COOR with any alkyl radical R), but preferably an aldehyde group (-CHO), and that for the Ν, Ν- Dialkylaminobenzen an organic solvent is provided which is transparent in the range of 337 nm, preferably ethanol, methanol, dimethyl sulfoxide, dioxane or tetrahydrofuran.