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Generation of microwave signals by optical heterodyning has been an active area of research in the field of Microwave Photonics. Though this approach offers great flexibility in choosing the microwave frequency, issues related to frequency stability and phase noise performance are inherent to it. The effect of laser phase noise on heterodyned output is mathematically analyzed, simulated and practically demonstrated. Design of hardware-efficient Optical Phase Locked Loop (OPLL) that overcomes the issues of phase noise and frequency instability is proposed. Frequency stability and phase noise tracking achieved by the proposed OPLL is demonstrated experimentally. Highly stable microwave signals, exhibiting phase noise as low as −105 dBc/Hz at 10 KHz offset (limited by the phase noise of the reference source used in the experiment), are successfully generated by the proposed approach. The generated microwave signals have been shown to be devoid of spurious components and harmonics.

A spectral optoelectronic system combining a collinear acousto-optic cell fabricated of calcium molybdate single crystal and a positive electronic feedback is proposed first and examined theoretically and experimentally. The feedback signal is formed at the cell output due to the optical heterodyning effect with the use of an unconventional regime of cell operation. It is shown that the feedback enables controlling spectral characteristics of the acousto-optic cell, resulting in enhancing the spectral resolution and the accuracy of optical wavelength determination. In the experiment, maximal filter passband narrowing was as great as 37 times.

A procedure for changing the spectral characteristics of injection lasers by Doppler-signal optical heterodyning by changing the injection current is discussed. Results of current tuning of the radiation frequency, coherence, and other characteristics of AlGaAs-heterolasers by using the above procedure under conditions of c.w. lasing are reported.

The USNO will undertake the construction and operation of a phase coherent, astrometric, optical interferometer which will be dedicated to the determination of stellar positions and motions. Building upon the experience gained from the MARK III Interferometer at Mount Wilson, the USNO instrument is currently in the very early stages of conceptualization and initial design. An abbreviated account of the experience gained with the MARK III is given. Examples of the issues and possibilities to be addressed in designing the new USNO instrument are outlined. Some background discussion involving interferometric techniques is included.

Des experiences de detection heterodyne ont ete effectuees, dans l'infrarouge, avec trois montages optiques differents un interferometre de Michelson modifie et deux montages utilisant l'amplification de la puissance retrodiffusee dans la cavite laser. A partir de la retrodiffusion sur un disque en rotation, on etudie la reponse du systeme en fonction de la frequence de battement. L'evolution du signal n.est pas lineaire. Cette non linearite provient de l'interaction de l'onde diffusee avec le milieu laser. A partir de ces resultats, on presente un prototype d'anemometre a laser capable de mesurer des vitesses de vent jusqu'a 40 km/h a une distance de 500 metres.

Heterodyne frequency measurements are reported for twenty optically pumped laser lines from various molecules including COF2, CD3F,13CD3F, and C2H5I.

The possibility to use narrow optical resonances and highly stable lasers as detectors of gravitational waves are discussed. The methods for measuring small displacements are based on the registration of small variations of a radiation frequency that arise in changing an optical phase. First results on the use of narrow resonances for precision measurements of small displacements are given. The achieved absolute sensitivity of the measurements amounted to 6·10−6 A on the basis of 5·102 cm.