Infrared heterodyne detection

F. R. Arams, E.W. Sard, B.J. Peyton, and F.P. Pace, Infrared Heterodyne Detection with... 

After briefly reviewing conventional optical and infrared heterodyne detection, we examine the behavior of a multiphoton absorption heterodyne receiver. Expressions are obtained for the detector response, signal-to-noise ratio, and minimum detectable power for a number of cases of interest. Receiver performance is found to depend on the higher-order correlation functions of the radiation field and on the local oscillator irradiance. This technique may be useful in regions of the spectrum where high quantum efficiency detectors are not available since performance similar to that of the conventional unity quantum efficiency heterodyne receiver can theoretically be achieved. Practical problems which may make this difficult are discussed. A physical interpretation of the process in terms of the absorption of monochromatic and nonmonochromatic photons is given. The double-quantum case is treated in particular detail the results of a preliminary experiment are presented and... 

J. B. Asbury, T. Steinel, C. Stromberg, K. J. Gaffney, I. R. Piletic, A. Goun, and M. D. Fayer, Phys. Rev. Lett., 9123, 7402 (2003). Hydrogen Bond Dynamics Probed with Ultrafast Infrared Heterodyne-Detected Multidimensional Vibrational Stimulated Echoes. 

Levenson, M. D., and Eesley, G. L. 1979. Polarization selective optical heterodyne detection for dramatically improved sensitivity in laser spectroscopy. Appl. Phys. 19 1-17. Librizzi, R, Viapianni, C., Abbruzzetti, S., and Cordone, L. 2002. Residual water modulates the dynamics of the protein and of the external matrix in trehalose-coated MbCO An infrared and flash-photolysis study. J. Chem. Phys. 116 1193-1200. 

As an example of three-frequency nonlinear heterodyne detection, we consider a CO2 laser radar operating at 10.6 (un in the infrared [7.14,61,62] (see Fig. 7.3). If we assume that we wish to acquire and track a 1-m-radius satellite with a... 

The widespread application of 10.6 pm heterodyne detection for communications, radar and infrared active imaging is presently restricted by the need to cool the detectors below temperatures obtainable from thermal electric coolers ( 180 K). Presently the main reason for cooling 10.6 pm heterodyne detectors is to reduce the thermal generation-recombination rate in the photoconductor or the diffusion current in diodes to a level that can be overridden by available laser local oscillator power. In general the use of photoconductors (with band gaps tailored for 10.6 pm radiation) seems to be a realistic approach to operation at 180 K or above. Since the thermal generation-recombination rate is of the order of 10 /t hole-electron pair per cm at 180 K it follows that a 1 pm thick, 10 cm area photoconductor with a carrier lifetime (t) of 10" s would require 1 milliwatt of LO power to approach hvB detector sensitivity at bandwidths of... 

In a heterodyne-detected transient-grating (HD-TG) experiment [5,8-11], two infrared laser pulses, typically obtained dividing a single pulsed laser beam, interfere within the sample producing an impulsive spatially periodic variation of the material optical properties. The spatial modulation is characterized by a wave vector which is given by the difference of the two pump wave vectors. The relaxation toward equilibrium of the induced modulation is probed by measuring the Bragg scattered intensity of a second continuous wave laser beam. A sketch of the experimental set-up and details on the laser systems can be found in ref 5 and ref. 10, respectively. 

Okamoto, H. (1998) High-sensitivity measurement of ultrafast transient infrared spectra based on optically heterodyned detection of absorption anisotropy. Chem. Phys. Lett, 283, 33-38. 

Hundreds of pure rotational lines of a variety of molecules have been detected in the interstellar medium, most of them in emission but some also in absorption. These lines occur throughout the millimetre, centimetre and decametre wavelength region of the spectrum and are detected using radio antennas and heterodyne detection techniques at spectral resolutions of typically 300 000. At submillimetre and far-infrared wavelengths, the atmosphere is not very transparent (Figure 1) and telescopes are located on high, dry sites, on airborne platforms or in... 

Fig. 5.9.1 A spectmm of the R(ll) line of ethane on Jupiter recorded with a CO2 laser infrared heterodyne spectrometer. LO marks the frequency of the laser local oscillator. The observed 25 MHz spectmm (histogram) was detected with a 64-channel radio frequency receiver at the output of the infrared detector mixer. The dashed and solid curves are calculations of the line shape (Kostiuk et al, 1987).

The sensitivity of heterodyne detection is limited by photon statistics at the infrared detector. The noise caused by the discrete, random arrival of photons is... 

Since multiple-quantum optical direct detection has also been studied in great detail, it seems natural to investigate the behavior of such a detector in the presence of more than one frequency [7.16]. In this section, we obtain the response and the signal-to-noise power ratio (SNR) for a multiple-quantum absorption heterodyne receiver, with particular attention devoted to the simplest case, i.e., the mixing of two waves in a double-quantum infrared or optical device. 

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