Optical cavity resonant frequencies

Laser - A device in which an optical cavity is filled with a medium where a population inversion can be produced by some means. When the resonant frequency of the cavity bears the proper relation to the separation of the inverted energy levels, stimulated emission occurs, producing a highly monochromatic, coherent beam of light. 

Some years ago D. Stuerga designed a microwave reactor, called the RAMO (reac-teur autoclave microonde), which is not a commercial device. The microwave applicator and the reactor are original. The resonant frequency of the cavity can be controlled by varying the position of a plunger. The effective cavity power can be increased by three orders of magnitude. The autoclave is made of polymeric materials, which are microwave transparent, chemically inert, and sufficiently strong to accommodate the pressures induced. The reactants are placed in a Teflon flask inserted within a polyetherimide flask. A fiber-optic thermometry system, a pressure transducer, and a manometer enable simultaneous measurement of temperature and pressure within the reactor. The system is controlled by pressure. The reactor is shown in Fig. 2.32. 

Free spectral range (FSR) The frequency difference between adjacent resonances of an optical cavity. 

An examination of the above equations shows that the intermodulated DFM technique realizes an FM Differential Interferometer which produces a locking signal similar to conventional FM laser locking, but in which the optical tuning parameter A=(0Q-2tr n c/2L is replaced by the radio frequency (differential) tuning parameter 5=(0j-2tr c/2L. The DFM sideband structure creates an optical subtraction in the photodiode of the (n+l)-th cavity resonance curve from the (n-l)-th curve and thus permits accurate, low noise measurements of the cavity mode spacing. 

If the nonlinear crystal that is pumped by the incident wave Ep is placed inside a resonator, oscillation on the idler or signal frequencies can start when the gain exceeds the total losses. The optical cavity may be resonant for both the idler and signal waves (doubly-resonant oscillator) or for only one of the waves (singly-resonant oscillator) [5.292]. Often, the cavity is also resonant for the pump wave in order to increase 7p and thus the gain coefficient T. 

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