After completing the "Cours Classique" at the Petit Séminaire de Québec, I enlisted in the physics program at Québec Laval University, obtaining a Bacc. ès Sciences in June 1960. Following a recommendation from Henri-Paul Koenig, then director of the department, I applied for and obtained a scholarship to study in Paris. There, I registered for the program in theoretical physics offered at the Institut Henri Poincaré, then directed by Louis De Broglie. After attending theoretical courses, my research focused on the possibility of observing corrections predicted by Einstein's theory of General Relativity in the motion of artificial earth satellites. In 1963, and after having expressed an interest in pursuing experimental physics after completion of the Doctorat d'Ëtat, Mme Marie Antoinette Tonnelat brought to my attention the effort by Joseph Weber at Maryland to detect gravitational waves. The existence of these had been predicted by Einstein but they had not been detected directly. Very interested, I applied immediately, was accepted, and arrived at College Park in May 1965. 

The lunar gravimeter experiment was proposed by Joseph Weber to NASA in the early sixties. The physics behind the experiment was that gravitational waves of appropriate frequencies could excite normal resonnant modes of the moon. The result would be vertical accelerations of the surface of the moon that a gravimeter could potentially detect. The frequencies involved are of one cycle per minute or less and were too low to be detected by seismographs. The gravimeter was to be built by a Texas company called Lacoste and Romberg Co. Weber was the principal investigator. The department of physics at Maryland was responsible for the design of the temperature control and the design of the electronics. As an incoming postdoctoral fellow, I accepted to search for a solution to the problem of maintaining the temperature of the gravimeter within 3 millidegree of the design 50 degree C through changes in the moon environment temperature in excess of 100 degree C. After 18 month of various calculations, I proposed a design that was approved by the Arthur D Little research company of Boston. At that point, I was listed as a NASA co-investigator on the project. Then, the system was built by the Bendix Corporation. The Lunar Surface Gravimeter experiment flew on the Apollo 17 mission, December 7, 1972. The instrument’s intended purpose was to look for gravitational waves, but a technical issue in the design of the Texas gravimeter meant that the unit was able to function best as a sensitive seismograph.

During that period, I raised the possibility of observing the general relativistic shift of a pulsar frequency during an eclipse (Physical Review Letter, vol. 21, no 21, 18 Nov 1968, 1483 (C))

After my work on the lunar gravimeter experiment, I felt that if piezo-electric crystal instrumentation of a bar antenna might permit Weber to observe very rare gravitational waves of very high intensity, that the coming of gravitational wave astronomy would require a very significant improvement in sensitivity. For that reason, I looked for a different type of instrumentation. By that time, Weber had tested a coupled electromagnetic resonance circuit to improve sensitivity and in 1974, H.J. Paik had introduced the concept of coupled mechanical resonance for the same purpose. At that point, and as a NSF co-investigator, I proceeded to develop a dc biased resonant capacitor transducer mounted at one end of the bar antenna with signal detected with FET electronics. Here, it became very important to redefine the noise temperature of an FET as the product of its voltage noise and its gate current noise. The latter is responsible for a back action on the antenna that raises the antenna noise level. That definition permitted to optimize the coupling needed between the antenna and the FET and, by this process, achieve the highest possible sensitivity given the antenna temperature, its mechanical quality factor and the noise temperature of the FET. These results were published in 1976 and a successful test was soon completed at liquid helium temperature. In 1979, I spent one year in Rome where such a system was further developed and used by the group on their 800 Hz bar antennas.

During the period 2007 to 2010, data was collected in Italy with the Explorer and Nautilus antennae operated at 2K. Both antennae used a capacitive electro-mechanical transducer such as introduced at Maryland earlier and used a Squid for electric signal amplification. A sensisitivy in h of a few parts in 10^-19/√Hz was reported, a remarkable achievement with a bar detector (Phys Rev. D 87, 23 April 2013).

From the early 70's into the early 80's, many groups in the US, Europe, Japan and elsewhere joined the effort to directly detect gravitational waves. Some used a Weber bar antenna, others used a Fabry-Perot or an optical delay line to achieve that goal. With a bar antenna, it appeared difficult to achieve a bandwidth of 25 Hz or more even with resonant coupling as described above. As a NSF co-principal investigator, I searched for a solution to both larger bandwidth and higher sensitivity. In a sole author paper of Jan 1979 (Perth, Australia), I proposed a detector consisting of serially connected three or more resonant oscillators of geometrically decreasing masses. Here, the bar antenna is the largest of these oscillators. I called such an instrument a multimode gravitational-wave detector. In such a detector, the gravitational energy deposited in the antenna by an incident gravitational wave is transmitted to the last and smallest resonator within a few milliseconds. It become possible to approach the quantum limit with a quasi-uniform sensitivity over a large bandwidth given appropriate temperature, resonators and electronics. I later descrived a five-mode system in general terms in the Physical Review Letters, vol. 52, no 3, p. 164 of Jan 16, 1982. It was hoped that such a detector operated at a sensitivity near the one phonon level and around 800 Hz could complement a 4-km laser interferometer such as the Laser Interferometer Gravitational Wave Observatory (LIGO) then being studied. My multimode bar detector concept was the object of a special citation by NSF (see Curriculum Vitae, 1980: Special Citation).

In a J. Appl. Phys. 64, 2202(1988) paper, I proposed to instrument the multimode gravitational-wave detector with an optical sensor. That research was carried as sole NSF principal investigator. Here, an 800 Hz bar antenna is coupled to 2, 3 or 4 coupled resonators. The last resonator includes a small super mirror of very high reflectivity and of weight of one gram that is part of a Fabry-Perot cavity. For such a small mass, optical power in the cavity can easily be obtained where the quantum noise injected in the last resonator by back action is of the order of the quantum noise in the readout. This is done while keeping the power dissipated in the optical cavity at the micro watt level or less. In this way, a sensitivity at the one-phonon level may be achieved if the noise in the antenna and the resonators is low enough. Here the temperature and the mechanical quality factors are determinant. In my Physical Review D paper (Vol 46, no 6 pp. 2309-2317 of 15 September 1992), in-house tests of a 100-micron long Fabry-Perot cavity are reported and approaching the one phonon sensitivity level with such an optical sensor on a bar system is analyzed.

Laser instrumentation can be operated at the shot noise level at power levels of the order of a fraction of a watt. The corresponding sensitivity in the measurement of small displacements with a Fabry-Perot cavity is very high. A stable clock can be obtained by locking a laser frequency to the length of a monocrystalline optical cavity. The length of that cavity can be stabilized to a very high degree by cooling to millikelvin temperatures. I understand that that concept I formulated in Rev. of Sci. Instrum. 62, 2375 (1991) is currently (2016) under development. The title of the article was: Cryogenic Monocrystalline Silicon Fabry-Perot Cavity for the Stabilization of Laser Frequency.