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Characterization of optical quality of GaSe:Al crystals by exciton absorption peak parameters

Konstantin A. Kokh 1,2,  Yurii Andreev 3,4,  Tatyana Izaak 4,  Gregory Lanskii 3,4,  Anna Shaiduko 3,4,  Valery Svetlichnyi 4

1. Institute of Geology and Mineralogy SB RAS (IGM), Koptyuga ave., 3, Novosibirsk 630090, Russian Federation
2. Novosibirsk State University (NSU), Pirogov 2, Novosibirsk 630090, Russian Federation
3. Insitute of Climatic and Ecological Systems of SB RAS (IMCES), 10/3 ave Akademicheskii, Tomsk 634055, Russian Federation
4. Tomsk State University (TSU), Lenina, 36, Tomsk 634050, Russian Federation

Abstract
It is well known that doping of GaSe crystals with isovalent elements: Al [1], S [2, 3], In [4, 5], Te [6, 7] and Er [8] strengthens the structure and improves optical quality , which in turn increases efficiency of parametric frequency conversion into mid-IR and THz ranges. On the other hand, excess doping leads to destruction of the lattice structure [9]. So it is obvious that intermediate optimal doping should exist. Direct search of this concentration by conventional spectroscopic measurements is very complicated due to low optical losses of GaSe in the range of maximal trabsparency (absorption coefficient ≤0.1-0.2 cm-1). Available data on the optimal doping in GaSe that resulted in the best optical quality and maximal conversion efficiency are limited by the only paper on tellurium doping [10]. The proposed method of characterization included two stages: (1) recording of absorption spectra of GaSe crystals with a set of doping concentration out of maximal transparency range, i.e. THz absorption spectra, (2) selection of a sample with maximal phonon peak intensities and narrowest spectral bandwidths. Optimal doping of selected samples was then confirmed by efficiency of SHG and optical rectification experiments. But to apply this method one needs quite rare and expansive facility. In this study we propose the recording of exciton absorption spectra by widespread and cheap UV-visible absorption spectrophotometer. Selection of optimally doped crystal can be carried out by: (1) choosing a crystal with maximal intensity and narrowest spectral bandwidth of exciton absorption peak, (2) choosing of a crystal with maximal gradient of the absorption end, and (3) with minimal absorption at the bottom of the absorption end (Fig. 1). Physical basis for this proposal will be discussed.

Fig.1. Characteristics of short-wave absorption diagram for Al-doped GaSe crystals.

In Fig. 1 it is seen that maximal intensity of the exciton absorption peak, minimal spectral bandwidth and absorption coefficient at the bottom of the short-wave absorption end are owned y 0.02 wt.% Al-doped GaSe crystals. Close characteristics are possessed by 0.05 wt.% of Al doped crystal. Thus, optimal Al doping has to be about from 0.02 to 0.05 wt.%. This proposal is confirmed by THz generation efficiency by optical rectification method.

References

1. Y.-F. Zhang, R. Wang, Z.-H. Kang, L.-L. Qu, Y. Jiang, J.-Y. Gao, Yu.M. Andreev, G.V. Lanskii, K.A. Kokh, A.N. Morozov, A.V. Shaiduko, V.V. Zuev AgGaS2- and Al-doped GaSe Crystals for IR Applications // Opt. Commun. 2011. V. 284. P. 1677-1681. 

2. K.R. Allakhverdiev, R.I. Guliev, E.Yu. Salaev, V.V. Smirnov Investigation of linear and nonlinear optical properties of GaSxSe1-x crystals // Sov. J. Quantum Electron. 1982. V. 12, No. 7. P. 947-948. 

3. H.-Z. Zhang, Z.-H. Kang, Yu. Jiang, J.-Yu. Gao, F.-G. Wu, Z.-S. Feng, Yu.M. Andreev, G.V. Lanskii, A.N. Morozov, E.I. Sachkova, S.Yu. Sarkisov. SHG phase matching in GaSe and mixed GaSe1-xSx, x<0.412, crystals at room temperature // Optics Express 2008. V. 16, № 13. P. 9951-9957.

4. D. R. Suhre, N. B. Singh, and V. Balakrishna, N. C. Fernelius and F. K. Hopkins Improved crystal quality and harmonic generation in GaSe doped with indium // Optics Letters. 1997. V.22, No.11. P.775-777

5. Z.-S. Feng, Z.-H. Kang, F.-G. Wu, J.-Yu. Gao, Yu. Jiang, H.-Z. Zhang, Yu.M. Andreev, G.V. Lanskii, V.V. Atuchin, T.A. Gavrilova. SHG in doped GaSe:In crystals // Optics Express 2008. V. 16, № 13. P. 9978-9985.

6. K.C. Mandal, S.H. Kang, M. Choi, J. Chen, Xi-Ch. Zhang, J.M. Schleicher, C.A. Schmuttenmaer, N.C. Fernelius. III–VI Chalcogenide Semiconductor Crystals for Broadband Tunable THz Sources and Sensors // IEEE Journal of Selected Topics in Quantum Electronics 2008. V. 14, № 2. P. 284-288.

7. Wei-Chen Chu, Shin An Ku, Harn Jiunn Wang, Chih Wei Luo, Yu. M. Andreev, Grigory Lanskii, T. Kobayashi. Widely linear and non-phase-matched optics-to-THz conversion on GaSe:Te crystals. Optics Letters, 2012, V.37, No.5, P.945-947. 

8. Yu-Kuei Hsu, Ching-Wei Chen, Jung Y. Huang, and Ci-Ling Pan, Jing-Yuan Zhang, Chen-Shiung Chang Erbium doped GaSe crystal for mid-IR applications // Optics Express. 2006. V.14, No.12. P.5484-5491

9. A. Gouskov, J. Camassel, L. Gouskov Growth and characterization of III-VI layered crystals like GaSe, GaTe, InSe, GaSe1-xTex and GaxIn1-xSe // Prog. Cryst. Growth Charact. Mat. 1982. V. 5. P. 323-413.

10. Shin-An Ku, Wei-Chen Chu, and Chih-Wei Luo, Yury Andreev, Grigory Lanskii, Anna Shaiduko, Tatyana Izaak, Valery Svetlichnyi, Kaung Hsiung Wu, T. Kobayashi. Optimal Te-doping in GaSe for non-linear applications. Optics Express, 2012, V.20, No. 5, P. 5029-5037. 

 

 

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Presentation: Oral at 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17, General Session 5, by Konstantin A. Kokh
See On-line Journal of 17th International Conference on Crystal Growth and Epitaxy - ICCGE-17

Submitted: 2013-04-14 10:50
Revised:   2013-07-17 11:14