Intracavity etalon

A 2-liter stainless steel vessel, partially filled with I2 crystals, was connected directly to the secondary He feed supply line of a supersonic chemical laser. A complete description is given in a separate paper.- The laser cavity had viewing windows on top and bottom so that the nozzle array could be viewed in a direction perpendicular to the optical axis. The pump laser was a Spectra-Physics Model 170-03 Ar+ laser equipped with an intracavity etalon. 

We have developed FM lasers based on a commercial ring laser (Coherent 699-21). In this case all the intracavity etalons are removed and replaced by a lithium niobate phase modulator. This modulator can be resonantly driven at a frequency close to the cavity mode spacing. A simple theory of FM operation of a laser suggests that the modulation index is given by [12]... 

Since the He-Ne is based on emission of gas-phase atoms, the frequency accuracy is excellent, and the output linewidth is sufficiently narrow for most Raman applications without special accessories such as an intracavity etalon. Like ion lasers, He-Ne lasers exhibit a variety of atomic emission lines from the DC discharge that must be filtered out before reaching the sample. 

A complete spectrometer setup is presented in Fig. 2.9. The stepping motor puts the grating into the wavelength region required. The intracavity etalon then selects the resonator mode and suppresses holeburning modes. It is scanned by a PZT. The resonator mode, finally is determining the laser frequency and it is tuned by another PZT. 

Fig. 5.36. Gain profile, resonator modes, and transmission peaks of the intracavity etalon dashed curve). Also shown are the threshold curves with and without etalon...

In the argon-ion laser the width of the gain profile is about 8 GHz. With a free spectral range of Av = c/(2nr) = 10 GHz of the intracavity etalon, single-mode operation can be achieved. This implies with n = 1.5 a thickness t = 1 cm. 

Fig. 5.56a,b. Discontinuous tuning of lasers (a) part of the neon spectrum excited by a single-mode dye laser in a gas discharge with Doppler-limited resolution, which conceals the cavity mode hops of the laser (b) excitation of Na2 lines in a weakly collimated beam by a single-mode argon laser. In both cases the intracavity etalon was continuously tilted but the cavity length was kept constant... 

Mode selection in an argon laser is often accomplished with an intracavity etalon. What is the frequency drift of the transmission maximum... 

W.R. Leeb Losses introduced by tilting intracavity etalons. Appl. Phys. 6, 267 (1975)... 

So far we have only considered the stability of the laser resonator itself In the previous section we saw that wavelength-selecting elements inside the resonator are necessary for single-mode operation to be achieved, and that then-stability and the influence of their thermal drifts on the laser wavelength must also be considered. We illustrate this with the example of single-mode selection by a tilted intracavity etalon. If the transmission peak of the etalon is... 

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