{"id":10694,"date":"2022-09-28T11:31:56","date_gmt":"2022-09-28T11:31:56","guid":{"rendered":"https:\/\/www.szlaser.com\/?page_id=10694"},"modified":"2022-09-29T12:21:37","modified_gmt":"2022-09-29T12:21:37","slug":"diode-laser","status":"publish","type":"page","link":"https:\/\/www.szlaser.com\/index.php\/wiki\/diode-laser\/","title":{"rendered":"An Introduction to Diode Laser"},"content":{"rendered":"

An Introduction to Diode Laser<\/h1><\/h1><\/div>

Laser diodes are well known for their applications in the area of communication technology, computer engineering, and entertainment electronics. These applications are based primarily on laser beam sources with powers in the milliwatt range. For some years, high-power diode lasers, with a power rating of up to several kilowatts, have been available. With these lasers \u2013 given certain limitations due to the attainable beam quality and energy density on the workpiece \u2013 machining tasks may be solved at moderate expense. In addition, high-power diode lasers, due to their special characteristics, can even open up new applications that were once considered unattractive or even impossible for lasers.<\/p>\n<\/div>

Diode laser bars<\/h3><\/h3><\/div>

Laser light with a power of several mW can be produced in a very thin and narrow zone (with a typical emitting area sized approx. 1 \u00b5m x 1 \u00b5m) by recombining the electron-hole pairs in a special semiconductor structure (based on GaAs). A variety of these elements may be combined in a semiconductor element to construct a laser bar approximately 10000 \u00b5m x 1200 \u00b5m x 115 \u00b5m. A typical emitting surface area consists of about 20 fields with approx. 25 single emitters each (Figure below). These single emitters of a field may also be combined to form a strip (wide-strip laser)<\/p>\n

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The laser resonator is formed by two fracture surfaces of the bar. The bars are coated to achieve the desired reflection properties, normally to a length of 900 – 1200 \u00b5m. The emitted laser radiation shows high divergence in the direction of the pn transition (\u201cfast axis\u201c) and, in the far field, has a Gaussian profile. In the direction parallel to the plane of the pn transition (\u201cslow axis\u201c), the radiation exits in the far field as a superposition product of the individual emitter groups (Fig. below).<\/p>\n

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Typical data of a cooled diode laser bar are summarized in the following table:<\/p>\n\n

\n \n \n\n \n \n \n \n\n\n wdt_ID<\/th> Output power<\/th> 30 - 60W<\/th> depending on mounting technology<\/th> <\/tr>\n<\/thead>\n \n\n \n \n\n \n \n \n \n \n \n
1<\/td>\n Wavelength<\/td>\n 808, 940, 980nm<\/td>\n other wavelengths possible<\/td>\n <\/tr>\n
2<\/td>\n Spectral width<\/td>\n approx. 4nm (FWHM)<\/td>\n <\/td>\n <\/tr>\n
3<\/td>\n Spectral shift<\/td>\n 0.25nm \/ \u00b0C<\/td>\n <\/td>\n <\/tr>\n
4<\/td>\n Thresh. current<\/td>\n 8 - 12 A<\/td>\n <\/td>\n <\/tr>\n
5<\/td>\n Efficiency<\/td>\n 35 -50%<\/td>\n electric-optical<\/td>\n <\/tr>\n
6<\/td>\n Quantum efficiency<\/td>\n 0.8 - 1.1 W\/A<\/td>\n Characteristical increase of the opt. \noutput power at current increase about the threshold<\/td>\n <\/tr>\n <\/tbody> \n\n \n \n \n\n <\/table>\n\n<\/div>