CW dye lasers

CW dye lasers are usually pumped wifh an argon ion laser, up to abouf f W of continuous dye laser power being produced, compared wifh abouf f MW peak power which may be produced in a pulsed dye laser. 

Ar+ lasers are robust, but the efficiency is low, f 0.05%. The heat generating additional turbulence near the telescope is a serious problem. They are now replaced with frequency doubled YAG lasers. These cannot yet deliver quite the same power at 532 nm, but they are much more efficient. CW dye laser systems have now been used to demonstrate Na LGSs at several observatories. 

ESO VLT/Max Planck CW Dye Laser. The MPI is developing a CW dye laser for deployment on one ESO 8-m VLT telescope in 2004 (Eig. 13). The oscillator is a Coherent 899 ring dye laser, with a 2-5 W output, pumped by a 10 W, Coherent Verdi frequency-doubled Nd YAG laser. The beam is amphfied in a four-pass amphfier with 4 high velocity dye jets pumped with 4 10 W Verdi lasers. The system utihzes Rhodamine 6G in ethylene glycol however, because of the high pump power, the dye degrades quickly, and must... 

In cw-dye lasers, pumped.by the focussed beam from an argon laser, linewidths of less than 20 Me/sec ( 10" A) have been achieved. 

Recent advances in constructing single-mode tunable cw dye lasers with a bandwidth of 20 Mc/sec or less 98a) open the way for high resolution absorption sepectroscopy without the limitations to fixed wavelengths 98b) One may observe either the total fluorescense intensity, which is proortional to the total absorption, or the decrease of the transmitted laser intensity. 

The last method has been pushed to an impressive sensitivity by putting the probe inside the cavity of a cw dye laser oscillating on several modes close above threshold. The sensitivity of such a broad-band dye laser to selective intracavity absorption on a single mode is proportional to the number of oscillating modes due to... 

P3/2-States of sodium, measured in a well collimated Na beam witn a cw dye laser... 

A crucial part of these experiments is the preparation of the sodium atoms into the excited state by laser optical pumping. A commercial single-mode Rhodamin 6G continuous wave (cw)-dye laser (Spectra Physics model 580) is used, having 20-40-mW single mode output power when tuned to the sodium resonance line. 

Gas-discharge lamps are used to optically pump the metastable helium atoms into a higher excited electronic state, which has a dipole-allowed transition to the ground state. Only He (2 S) can be pumped selectively, thereby producing pure He(23S) beams. For the heavier rare gases, both metastable states are equally pumped by gas-discharge lamps. The use of cutoff filters to selectively pump one state is not adequate because of the temperature dependence of the filter transmission and the low / numbers of the pumping transition. Metastable neon can be selectively pumped by a continuous wave (cw) dye laser,60 whereas Ar, Kr, and Xe have so far only been selectively pumped by pulsed dye lasers.61... 

Fig. 12.1 Thermionic diode and cw dye laser used by Weber and Niemax to measure Cs self...

Observation of optical fluorescence,with frequency doubled CW dye laser D2 line of Ra first data taking Nov. 85 (IP-16)... 

The effect of mode competition, which is generally the dominant effect, is more subtle since, to a first approximation, a cw dye laser has only one mode. Theories of IDLS which account for mode competition have been put forward by Hansch, Schlawlow, and Toschek (HST) and by Brunner and Paul (BP). HST start with a realistic set of laser rate equations but use substantial approximations to solve them. BP use an approximate and very empirical set of rate equations which they solve analytically. Each theory yields a prediction for the dependence of enhance-m it on pumping power P relative to the threshold pumping power... 

Intracavity absorption by I- vapor has been studied for a cw dye laser. The sensitivity enhancement varies from l(r at pump powers near threshold (550 mW and 790 mW) to about 500 at the highest pump powers (near 5 watts). The results can be interpreted quantitatively in terms of a previously proposed theory. 

In 1986, R. BEAUSOLEIL and D. McINTYRE completed their thesis research at Stanford with an absolute frequency measurement of the F = 1 component of hydrogen 1S-2S [11,20], As frequency reference they employed a 486 nm cw dye laser, locked to a narrow absorption line of 1J Te2 vapor. This line was chosen near a reference line, calibrated to within 4 parts in 1010 by A. FERGUSON et al. [21]. Its second harmonic coincides very nearly with the resonance frequency of the hydrogen two-photon transition, so that the frequencies can be precisely compared by observing a radio frequency beat signal. 

Figure 11.28. Energy level diagram and observed transitions for the microwave/optical double resonance spectrum of CuF. Optical excitation was accomplished using a rhodamine cw dye laser, pumped by an argon ion laser [53],...

Figure 11.51. Nj ion beam laser fluorescence spectrum near the bandhead of the B 2 + X 2 + ( 0,1 ) band, obtained by scanning the frequency of a cw dye laser [99].

As reported earlier (18), the QRLPP effect is a threshold process, requiring sufficiently high atomic density N and laser intensity I. The threshold values depend on various parameters like laser detuning and bandwidth, focusing optics, and the particular excited state involved also, the threshold N and threshold I values are correlated, with the increase of one allowing a decrease of the other. Typical threshold values in Cs are N=10i cm and I=10 W cm when a 6010A laser is used to excite the 5(803 2) state. Threshold values when other states are excited or when other alkali vapors are used can be quite different for example, Stwalley and co-workers (19) have reported that the threshold values in a sodium vapor are N lQt cm and I 10 W cm when a focused cw dye laser at 5688 or S683A is used to excite the Na(4D) state. 

The availability of suitable cw dye lasers is somewhat limited and for many systems pulsed dye lasers have to be used. The obvious difference is that the relative concentration of the radical is obtained for only one time-delay each time the photolysis laser is fired. Thus, the production of a full decay curve, of say 100 points, can take considerably longer than with a cw probe laser. Figure 2.5 shows how a decay trace is built up in these experiments. 

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