On the opto-voltaic measurements in CO and CO2 lasers

Abstract

Abstract. We observed and compared the opto-voltaic signals in CO and COz lasers. The signals are obtained capacitively from the water cooling jacket as a low voltage source not influencing the current circuit. We observed from measurement that the output power and the so-called optovoltaic input power have a distinct relationship depending on laser current and cavity parameters. It will be shown that opto-voltaic detection is a very sensitive method especially for CO lasers. PACS: 42.55, 42.60, 42.80 The phenomenon of static resistance fluctuation in a cw laser discharge due to the intra-cavity coherent radiation is well-known as opto-voltaic or optogalvanic effect [1]. It was used succesfully for stabilizing a single line CO2 laser with high accuracy [1,2], the alignment of a laser cavity [3], and the detection of radiation [4] in COz lasers. In general, the resistance fluctuations of the discharge due to laser-action in a current stabilized or ballast resistor regime results in fluctuations of the power that is dissipated in the discharge, and hence in temperature variations of the plasma and the discharge tube. We shall analyze and compare the opto-voltaic effects in CO and COz lasers having intra cavity modulation. It will be shown that the potential of the cooling water jacket which is capacitively coupled to the plasma is equal to half the maximum opto-voltaic value of the discharge.

Construction and operation of high power gas lasers

“…It can be used successfully for stabilizing a single line CO 2 laser with high accuracy [3][4][5], the alignment of a laser cavity [6], and the detection of radiation [7] in CO 2 lasers. In general the resistance fluctuations of the discharge due to stimulated emission in a current stabiliTed or ballast resistor regime result in fluctuations of the power that is dissipated in the discharge, and hence in temperature variations of the plasma and the discharge tube.…”

“…We detect the opto-voltaic signal in the water-jacket by putting a needle-shaped probe in the water tube close to the water-jacket [5]. The signal $2 in fig.…”

Noncontact optogalvanic signal detection in DC discharge CO2 lasers

“…which, in fact, makes up a coaxial capacitor together with a discharge column [19]. The presented work employs a similar method but uses either a conductive cover or a rod placed around the discharge tube.…”

“…Also, a needle-shaped Cu probe was inserted into the cooling-water jacket and similarly connected to the oscilloscope to obtain the OG signals, as described in [19]. In addition, an Al foil envelops the discharge tube as a cover.…”

“…Upon the first application of lasers in optogalvanic (OG) studies [1], the laser optogalvanic effect found widespread application in various fields [2][3][4][5][6][7][8][9][10][11]. As regards CO 2 lasers, all microscopic laser-plasma processes occurring in such active mediums have been well studied [12][13][14][15], and various OG signal detection methods in DC and RF discharge tubes have been discussed in details [16][17][18][19][20][21]. Moreover, both the dependence of the OG signal phase and amplitude on the laser modulation frequency [22][23][24] and the temporal behavior of signal shapes [25][26][27] have been theoretically and experimentally studied in many previous works.…”