Photo-induced structural and physico-chemical changes in amorphous chalcogenide semiconductors

Owen, A.E.; Firth, Adam; Ewen, Peter

doi:10.1080/13642818508240606

Cited by 246 publications

(65 citation statements)

References 45 publications

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“…The transmission generally decreased with time, approaching a saturation level for long exposures. Figure 3 illustrates the result of photodarkening of the laser-deposited films at various laser intensities in W/cm 2 and exposure time expressed in units of laser fluence J/cm 2 . We have divided the exposure/intensity map into three distinctly different regions: no photodarkening, re- versible, and permanent photodarkening.…”

Section: Photodarkening Characteristicsmentioning

confidence: 99%

“…1 Chalcogenide glasses are also frequently sensitive to optical radiation and show a wide variety of photoinduced effects as a result of illumination. [1][2][3] Various models have been put forward to explain these effects, [4][5][6] and the index change accompanying the common photodarkening phenomenon can be used to fabricate diffractive as well as waveguide structures. [7][8][9][10] Up to now, thermal evaporation and sputtering have been used to create the chalcogenide glass thin films.…”

Section: Introductionmentioning

confidence: 99%

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Low-loss waveguides in ultrafast laser-deposited As_2S_3 chalcogenide films

et al. 2003

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Section: Photodarkening Characteristicsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Low-loss waveguides in ultrafast laser-deposited As_2S_3 chalcogenide films

et al. 2003

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“…Chalcogenide glasses are well-known IR--transmitting materials [14]. They exhibit a wide range of photoinduced eects accompanied by signicant changes in their optical constants, that enable them to be used as optical recording or imaging media [15], absorption lters, and many other optical elements [16]. Knowledge * corresponding author; e-mail: dr_isyahia@yahoo.com of the optical properties of amorphous materials are obviously necessary for exploiting these materials in very interesting potential technologies.…”

Section: Introductionmentioning

confidence: 99%

Validity of Swanepoel's Method for Calculating the Optical Constants of Thick Films

2012

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Optical constants, dispersion and oscillator parameters of dierent thicknesses of amorphous Ge25Cd5Se70 lms have been deposited onto glass substrates using thermal evaporation technique. The optical constants have been investigated by optical spectrophotometry measurements. The straight forward analysis proposed by Swanepoel, which is based on the use of the extremes of the interference fringes has been used in order to derive the refractive index and the lm thickness in µm range. The refractive index could be extrapolated by the Cauchy dispersion relationship over the whole spectral range, which extended from 400 to 2500 nm. It is observed that, refractive index n increases with the lm thickness. The possible optical transition is found to be allowed indirect transition with energy gap increase from 1.915 to 1.975 eV with increasing lm thickness. The dispersion of the refractive index is discussed in terms of the WempleDiDomenico single oscillator model. The interband oscillator wavelength, the average oscillator strength, and the optical conductivity were estimated for dierent thicknesses of amorphous Ge25Cd5Se70 lms.

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“…Superficially similar photorefractive effects are well know in other chalcogenide glasses such as those based on arsenic and germanium sulphides [5,6]. In such glasses the photo induced index changes are often accompanied by changes in density, usually photodensification.…”

Section: Resultsmentioning

confidence: 77%

Laser Ablation Deposition of Ga2S3-La2S3 Glass Films

1995

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Gallium -lanthanum sulphide glasses (GLS) show wide range transparency and low non radiative relaxation rates for dopant ions such as Ho", EI' etc. They also show permanent photomodification of the refractive index under visible illumination. We report laser ablation deposition of these glasses and preliminary results on film stoichiometry and deposition rate as a function of excimer laser fluence. The sulphur to metal and G&a ratios are found to have marked fluence dependencies. The films show considerably more Urbach tail absorption than bulk material. A novel method has been developed for mapping the permanent photomodifled index. INTRODUCTJONGallium-lanthanum sulphide (Ga&La$,) ('GLS') glasses [l] have a range of novel optoelectronic applications. The material is transparent from -0.65um to -lOurn, covering the important near infrared telecommunications and mid infrared 'fingerprint' spectral regions. The lanthanum content ensures very high solubility for other rare earth dopant ions such as Er3',Ho",Pr3',Nd" [2] etc which can be used as active laser or optical amplifier species. The low phonon energy of GLS glass gives rise to low non radiative relaxation rates, which opens the possibility of operating lasers in this host material in the mid infrared. Laser action to wavelengths approaching 5um may be feasible in high quality films. An unusual property of the material is that the refractive index can be substantially and permanently modified by exposure to illumination above the band gap, typically at 0.5145pm wavelength or shorter [3,4]. FILM DEPOSITION Target fabricationThe use of these large targets ensures consistency of target material over mAblation targets are manufactured as gallium lanthanum sulphide glass disks of typically 40mm diameter by 1Omm thick. any ablation experiments and freedom from target thermal damage and cracking. Gallium sulphide (70% molar) and lanthanum sulphide (30% molar) are weighed out under dry nitrogen into a vitreous carbon crucible pre placed in a silica ampoule. Particular care is taken with the source of the sulphide (Merck) to minimise contamination with oxysulphides. The silica ampoule is evacuated and heated to 1200C for two hours and then water quenched. The glass disc is clear orange/yellow, with some superficial bubbles where gas adhered to the crucible/glass interface.The discs release easily from the crucible and there is no evidence of attack. The targets are visually homogeneous and show visible and IR spectra typical of GLS glass. Energy dispersive X ray analysis shows the targets to be homogeneous and stoichiometric to within experimental error. The disc is ground down to a flat surface, cleaned, and mounted in a cup designed to provide a surface to radiate the absorbed power load and minimise conduction to the in-vacuum stepper motor drive.

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Photo-induced structural and physico-chemical changes in amorphous chalcogenide semiconductors

Cited by 246 publications

References 45 publications

Low-loss waveguides in ultrafast laser-deposited As_2S_3 chalcogenide films

Low-loss waveguides in ultrafast laser-deposited As_2S_3 chalcogenide films

Validity of Swanepoel's Method for Calculating the Optical Constants of Thick Films

Laser Ablation Deposition of Ga2S3-La2S3 Glass Films

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