Effect and optimization of the diminution of the sensitizing intensity in two-center recording

Abstract

The effect of the diminution of the sensitizing intensity from initially high value on two-center recording is experimentally and theoretically investigated. A linear diminution of the sensitizing intensity is designed, and three different diminution rates are employed for the experimental investigation. The results show that the dynamic range can be improved by reducing the diminution rate of the sensitizing intensity. Compared with that of traditional two-center recording, the recording sensitivity obtained in the experiment is more improved when the maximum dynamic range is achieved. The effect of the diminution of the sensitizing intensity on grating uniformity and the effect of the initial sensitizing intensity on the recording sensitivity are theoretically investigated.OCIS codes: 090.2900, 160.3730, 160.5320, 210.2860. doi: 10.3788/COL201210.060901.The two-center holographic recording method reported by Buse et al. has attracted attention because of its ability to record persistent holograms [1] . The advantage of this method from other grating-fixing methods is its alloptical, real-time process [2,3] . The two-center recording method uses two different dopants to produce shallower and deeper traps in photorefractive crystals. The key point of this technique is that, during the recording of an interference intensity pattern by two beams with longer wavelengths, the crystal is simultaneously sensitized by a beam with a shorter wavelength so that an inner-field grating can finally be built in the deep center, which is insensitive to the recording beam for further readout.Much work has been done to improve the recording sensitivity and dynamic range in two-center recording. The effect of the dopant element and its concentration, annealing, and recording and sensitizing intensities and wavelengths on these parameters has also been investigated [4,5] based on stable recording and sensitizing intensity values. Researchers have observed that, for doubly doped LiNbO 3 crystals, the recording sensitivity monotonously increases as the intensity ratio (I R /I S ) decreases. Meanwhile, the dynamic range increases to a maximum value at a certain intensity ratio and then monotonously decreases. The maximum dynamic range usually sacrifices the recording sensitivity [6−8] . However, a mass-storage system is necessary to improve the recording sensitivity.In this letter, we utilize the diminution of the sensitizing intensity to optimize two-center recording. The recording sensitivity is well known to be directly proportional to the average electron concentration (N − 20 ) in the shallow center. Similarly, the dynamic range is directly proportional to N − 20 /n 0 , where n 0 is the average electron concentration in the conduction band [7] . The enhancement of N − 20 and n 0 depends on the improvement of the sensitizing intensity. If the sensitizing intensity is reduced from a high initial value to optimize two-center recording, a high recording sensitivity can be achieved at the start of the recording process. Then, the d...

Crystal growth, spectroscopic characterization and laser performance of Tm/Mg:LiNbO3crystal

“…The excellent combination of electro-optical, acoustooptical and nonlinear optical properties of lithium niobate (LiNbO 3 , LN), combined with the possibility of rare-earth doping, makes this host an attractive material for application in integrated optics [10][11][12][13][14][15][16]. Laser action at 1.85 µm in Tm:LN was first demonstrated at 77 K 43 years ago in a bulk-doped sample [3].…”