ISSN:
1432-0649
Keywords:
07.65.-b
Source:
Springer Online Journal Archives 1860-2000
Topics:
Physics
Notes:
Abstract Low-wavelength modulation (1 kHz), high-wavelength modulation (100 MHz) and two-tone frequency modulation (390±5 MHz) spectroscopies are systematically compared by measuring the minimum detectable absorption achieved using an AlGaAs diode laser tuned on a third-overtone methane transition at 886 nm. From the S/N behavior has been extrapolated a minimum relative absorption (1 Hz of bandwidth) of 4.5(1)×10−7 for the LMW, 9.7(3)×10−8 for the HWM and 6.4(2)×10−8 for the TTFM. In the LWM case the detection-limit value is represented by the laser amplitude 1/f excess noise, while for the high-frequency detection techniques this contribution is negligible with respect to other noise sources. These detection limits well agree with the calculated “quantum limited” values based on measured laser power, modulation index, noise figure of the electronic components, and other parameters of the apparatus.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00325250
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