Terahertz quantum cascade laser - Terahertz Quantenkaskaden-Laser

Collaboration with - Zusammenarbeit mit LASER COMPONENTS GmbH
 
 
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Collaboration with LASER COMPONENTS and University of Neuchatel

Mode profile of laser L2 for different distances between detector and laser, some artifacts appear due to fringes in the windows of detector and laser.

See our paper for more details: E. Bründermann et al., Turn-key compact high temperature terahertz quantum cascade lasers: imaging and room temperature detection, Opt. Express 14, 1829-1841 (2006), Free pdf download at Optics Express

Video of real-time measurement

   

Video of a live measurement over 200 seconds with changing trigger modulation (see description of screenshot below) of the pulse train and with inserted object like paper and metal plate (MPEG4 video compressed in time by a factor of 4: 50 seconds running time).

Quanta-Tera.avi (427 kByte)

Joined article with LASER COMPONENTS in Journal Photonik: www.photonik.de
Free PDF (473 kByte in German): Erster mobiler stickstoffgekühlter Terahertz-Quantenkaskadenlaser.

Screenshot of completed data acquisition with Golay detector and THz quantum cascade laser

 A pulsetrain of 300 ns long THz laser pulses with a repetition rate of f = 10 kHz is incident on the Golay detector. Due to the slow response time of the Golay detector this pulse train was electronically modulated at a lower frequency fM (electronic chopping). For more information on electronic chopping measurements see Fig. 10 in our paper (Free pdf download at Optics Express). Note, that the average power of the laser is always the same for different modulation frequencies fM. The signal drop in the measurement is only due to the response time of the Golay detector or the inserted materials (paper, metal). The average power can reach up to 5 µW for a pulsetrain of f = 90 kHz.

Screenshot of completed live measurement using a NI LabView program for data acquisition:

The measured sequence, parameters change approx. every 10 seconds, corresponds to the following modulation frequencies fM/Hz = 50, 40, 30, 20, 10, 5, 10, 10 and inserted paper sheet, 5 +paper, 10 +paper, 10, 10 +metal plate to show signal zero level, 10, via 20, 30 and 40 back to 50. The product of signal level at the detector and modulation frequency is roughly constant. At 5 Hz (without paper between 60 and 70 seconds) the signal level would correspond to 16 Volt which is clipped by the maximum input voltage (10 V) of the National Instruments USB A/D converter (NI USB-6009). At 10 Hz with the paper sheet inserted we obtain approximately the same signal level in comparison to the 50 Hz value which suggests a five times reduction due to absorption or a THz laser power absorption of 80% around 3.5 THz.

 
 
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