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Q: Fachverband Quantenoptik und Photonik

Q 43: Optische Messtechnik

Q 43.3: Vortrag

Mittwoch, 21. März 2007, 14:30–14:45, 5E

Optical frequency measurement in the mid- and far-infrared range — •Peter Gaal¹, Markus Raschke^1,2, Klaus Reimann¹, and Michael Wörner¹ — ¹Max-Born-Institut, Berlin, Germany — ²Department of Chemistry, University of Washington, Seattle, USA

We present a new method for the direct measurement of optical frequencies in the mid- and far-infrared range, which is analogous to a sampling scope. The electric field of an arbitrary source is measured by electro-optic sampling using 12 fs light pulses as a probe from a Ti:sapphire oscillator. The oscillator pulse length determines the upper bandwidth limit of 40 THz. The sampling rate is given by the oscillator repetition rate of 71 MHz. While measuring the time dependent electric field would require a synchronization of the source to the probe pulses, our method can be applied to an unsynchronized source. As a demonstration we investigate a cw CO₂ laser. Since the laser is not synchronized to the probe pulses, the electro-optic signal has to be recorded for each pulse. While we measured a spectral width of 90 kHz for an accumulation time Δ T of 0.7 s, it was reduced to 600 Hz for Δ T=1 ms. The fluctuations are caused by the thermal instability of the resonators of the oscillator and of the CO₂ laser.