AAWSAP DIRD, High-Frequency Gravitational Wave Communications, April 2010

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2.2 HFGW DETECTORS (RECEIVERS)
2.2.1 Alternative Approaches
One of the first suggested means for the detection of HFGWs concerns electromagnetic
detectors (Braginsky, et al. 1974 and Braginsky and Rudenko, V, 1978). Then
Pegoraro, et al. (1978) suggested the use of tuned resonant chamber HFGW detectors.
Rudenko and Sazhin in 1980 proposed a Laser interferometer as a gravitational wave
detector (somewhat similar to the current Japanese approach). In 1995 Tobar
characterized multi-mode resonant-mass HFGW detectors and three years later in 1998
(Ottaway, et al.) proposed a compact injection-locked Nd :YAG laser for HFGW
detection. And in 1999 Tobar suggested, microwave parametric transducers for the
next generation of resonant-mass gravitational wave HFGW detectors.
In the past few years, HFGW detectors have been fabricated at Birmingham University,
England, INFN Genoa, Italy and in Japan. These types of detectors may be promising
for the detection of the HFGWs in the GHz band (MHz band for the Japanese) in the
future, but currently, their sensitivities are orders of magnitude less than what is
required for the detection of high-frequency relic gravitational waves (HFRGWs) from
the big bang. Such a detection capability is to be expected, utilizing the Li-Baker
detector (please see Appendix B for Plans & Specifications development). Nevertheless,
all four candidate detectors; plus, possibly, the use of superconductors (Li and Baker,
2007) should be analyzed for possible military applications. The Li-Baker HFGW
detector was invented by R. M L Baker, Jr. of Transportation Sciences Corporation,
California and patented in P. R. China (Baker, 2001). Based upon the theory of Li, Tang
and Zhao (1992) termed the Li-effect, the detector was proposed by Baker during the
period 1999-2000, a patent for it was filed in 2001, subsequently granted (Baker,
2001), and preliminary details were published later by Baker, Stephenson and Li
(2008a). This detector was conceived to be sensitive to relic HFGWs (HFRGWs) having
amplitudes as small as 10-32 to 10-30 .
The Birmingham University HFGW detector measures changes in the polarization state
of a microwave beam (indicating the presence of a GW) moving in a waveguide about
one meter across (see Figure 9). Also see Cruise (2000), Ingley and Cruise (2001) and
Cruise and Ingley (2005). It is expected to be sensitive to HFGWs having spacetime
strains of A ~ 2 x 10-13 (Hz)·½, where Hz is the GW frequency, and as usual A is a
measure of the strain or fractional deformation in the spacetime continuum
(dimensionless m/m).
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