High resolution and medium resolution VIS OPOs


LaserSpec nanosecond VIS OPO’s, SHG and THG units are built using BBO, and LBO with bandwidth narrowing intracavity etalon plate. The simplicity of the design means high conversion efficiency, simple operation and rugged mechanics. The bandwidth of the OPO can be adapted from a few ~3cm-1 to 0,02 cm-1. The OPO are continuously tunable from 205 nm to 2600 nm.


The scanning performances of the medium resolution OPO are illustrated in the following figures.









Molecular spectroscopy.


The “user” set up is located in the “user” room at about 10 m from the OPO located in the “laser room”. The VIS-OPO is pumped by a multi-mode YG980 Nd:YAG laser, 10 Hz, between 100 and 200 mJ@355nm.


Toluene is chosen as “a test” molecule and is mixed in Argon in a pulse molecular beam synchronized with the OPO at 10 Hz. The molecules are ionized by the frequency doubled VIS-OPO laser beam @ 262 nm and detected by a time of flight mass spectrometer.


1) Broadband mode (bandwidth is 2 cm-1 FWHM)

Repeated ionisation in broadband mode (peak saturation above 1 a.u.)


2) Medium resolution mode (bandwidth is 0,15 cm-1 FWHM)

This band near 37620 cm-1 is constituted by a set of peaks as shown in the next graph. This peak structure does not allow testing the VIS-OPO resolution, but the VIS-OPO is able to measure the band shape. The width of the band measure with the OPO is 6 cm-1 width, three times that of the band shown in the literature, indicating that hot “molecules” are still present in the laser beam-gas interaction zone. The spectrum is expected to be an addition of structures resembling that presented in the literature but slightly shifted towards the “red”. The reproducibility of the band shape demonstrates the resetability of the OPO while the detection of substructure demonstrates sub cm-1 bandwidth.