Canterbury Ring Laser and Tests for Nonreciprocal Phenomena

Abstract

An historic and simple experiment has been revitalised through the availability of supercavity mirrors and also through a heightened interest in interferometry as a test of physical theory. We describe our helium-neon ring laser, and present results demonstrating a fractional frequency resolution of 2�1x10-18 (1�0 mHz in 474 THz). The rotation of the earth unlocks the counterrotating beams. A new field of spectroscopy becomes possible, with possible applications to geophysical measurements such as seismic events and earth tides, improved measurements of Fresnel drag, detection of ultraweak nonlinear optical propert~es of matter, and also searches for preferred frame effects in gravitation and for pseudoscalar particles.

Ring-laser tests of fundamental physics and geophysics

“…A recent facility is the C-I ring-laser system designed by Professor Hans R Bilger of Oklahoma State University, Stillwater, OK, USA and built at the University of Canterbury, Christchurch, New Zealand (Stedman et al 1993, Anderson et al 1994 figure 6(a)). This He-Ne ring laser system (f 0 = 473.6 THz, λ = 633.0 nm) is defined by a rectangle of four supermirrors, nominally 99.9985% reflectors and having measured total losses at manufacturing in the range 8-14 ppm, of which up to 10 ppm constitute the (designed) transmission loss, and 3-5 ppm are measured as scattering loss.…”

“…All proposals known to us consider square rings. The use of one extra mirror over the minimal triangle has advantages in reducing backscatter through the near-ideal incidence angle of 45 • , in permitting alternative choices of polarization, and in maximizing the signal/loss ratio A/P N, where N is the number of mirrors and, as before, A is the area and P the perimeter (Stedman et al 1993). In addition, the s reflectivity of a supermirror designed for normal incidence is in fact greater at 45 • incidence than at either the design angle of 0 • or the angle appropriate for a triangular ring (30 • ).…”

Rotation Sensing Lasers in General Relativity: Some Technical Notes and Current Advances

“…Ring laser gyroscopes capable of measuring Earth rotation came much later [8] and over the last twenty-five years have increased in size between 1 and 834 m 2 [9]; more recently, these have employed short wavelength neon transitions in order to maximise the scale factor of the device via the optical frequency [10]. Of the wide variety of different laser systems constructed over the years [4], they all share common features such as radio frequency excitation of a helium-neon gain medium which fills the entire optical cavity, which itself has no other hard apertures or other optical elements apart from the intra-cavity supermirrors.…”

Closed-loop locking of an optical frequency comb to a large ring laser

“…As a consequence, in little more than 15 years, laser gyroscopes increased in size from 0.748 m 2 [9] to 834 m 2 [10]. A laser gyroscope senses rotation through the Sagnac effect.…”