Undirectional Ring Ti/sup 3+/: AL/sub 2/O/sub 3/ Laser Operation at the Wavelength of an Atomic Absorption Line Using Bi-Directional Passive Self-Injection

Passiw self-injection locking (PSIL) laser spectral control yields efliciency close to thal in the oplimiied xion-selective cavity and avoids the optical damage ofthe selectors [1,2] Its principle lies in the spectrally selective re-injection in the cairity of a pall of the output beam \I" SIIDI\ (theov, experiment) that such control entails 8s addition the principle of novel technique for producinq in a purcly optical and simple manner hish power unidirectional ring l a w generatm Mhich is spectrally fixed at a chosen reference atomic absorption lux Such lasers are of interest as wavelength standards. in laser isotope reparation and In DIAL lidars We use the unbalance between two competitiw wavelength scanned passive selfinjections, that is produced by the absorption at the reference line (Fig 1 J In a faur-mirror ring cur Ti:AI?O> laser cavity (AI' pumping. output mirror M 4 with RzO9S). the first passive self-injection enforces the oscillation in the counter clockwise directed wave in the Ti A207 crystal (CCW-wave, output p o w r Pccw. tofal generated power in both 9'" . . . waves Plot) It is icalired by the 4% reflection back of the clockwcse (CWi wave output light uimg the wedged glass plate Mr The second self-injection i s realized by rn,ieition of the CW output beam parsing through Mr intu the ring ca\:ty in the C\V wave This injection is \,ia the optical line formed by the Faraday Isolator F1 (Glan piisnr G: . polarization medium P,W, second Glan prism G 2 , tranbnussion iii GIG: direction). the rem-reflrctmg mirror M a . and the intermediate miim M i A half-wave plate (h:? plate between M-I and hll ) ensures the full reflection by the prism G i ofthe CCW output beam out of the optical line (Output?.) The selection of the wavelength of the reinjections (the same far both beams) and the tuning are realized by the interference wedge (IN' between hh and M r J A medium with thc reference line AM is placed betueen GI and Mr The ratio ofthe powers of the twu re-injected beams ( d e d by adjustment of Mi) i s chosen to ensure unidirectional E o ' p operation in C W direction beyond the absorption line ; When the wavelength is tuned to the reference linc, due to P the absorption. this ratio is inverted and the laser oscillates 7 uni-directionally in opposite (CCW) direction at the d '' wavelengh of thc re-injection (Output 2) If the watelengh of the re-injection is scanned repeatedly around the reference Ime. the ring laser producer from its Output 2 pulsed emission spectrally fixed at the reference line The repetition rate and the pulse length are determined by the repelition rate and the speed of the scanning. respectively During the locked generation AM is practically not illurmnated. The theoretical analysis gives a considerable narrowing ofthe locked line m comparison with the line-width of the absorption. In the experimental check (Fig 2) with lid":YAG crystal as AM (absorption line 798,s nm), 5 Hz repetition rale, 0.2 W aver output power. IW ms pulse-length locked emission a1 this line is obtained (the scanning i s realized by forward-backward movement of the IN' in its plane) REFEREHCESAM Neveux,M Nenchev.R Barbe.! C Keller, IEEE J Quam Electron 3 l(1995J I253-1260,2.M Dene\,a.D Slavov,E Stoykova,\4 Yenchev,Opt.Communs, 330(1997)287-298 ,~ . .~. . , uu~r'i RS.1