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Materials for Laser Frequency Conversion

#2444


New Materials for Laser Frequency Doubling System Based on the Non-Stoichiometric Chalcopyrite Structure Crystals

Tech Area / Field

  • MAT-ELE/Organic and Electronics Materials/Materials
  • PHY-OPL/Optics and Lasers/Physics
  • PHY-SSP/Solid State Physics/Physics

Status
3 Approved without Funding

Registration date
05.03.2002

Leading Institute
Institute of General and Inorganic Chemistry (IONKh), Russia, Moscow

Supporting institutes

  • Lomonosov Academy of Fine Chemical Technologies, Russia, Moscow\nNPO Astrophysica, Russia, Moscow

Collaborators

  • Brookline Technologies, USA, New York\nCSSD-Centro di Studio per la Strutturistica Diffrattometrica/Consiglio Nazionale Delle Ricerche, Italy, Parma\nUniversity of California/Depertment of Materials Science, USA, CA, Berkeley\nDel Mar Ventures, USA, CA, San Diego\nUniversität Osnabrück, Germany, Osnabrück

Project summary

Project goal is the elaboration of new technology of nonlinear cadmium-germanium diarsenide crystal growth from non-stoichiometric solution–melt, which allows to produce the pilot samples with sufficiently higher non-linear optical properties in comparison with known materials.

A large amount of nonlinear crystals which dispersion of refractive index will allow its application to realize different parametrical processes are known to date.

Actually, gallium selenide (GeSe), silver selenogallate (AgGaSe2) and zinc germanium phosphide (ZnGeP2) and cadmium-germanium diarsenide (CdGeAs2) are used in the setups of total and difference frequency mixing, as well as in the parametric light generators.

Cadmium-germanium diarsenide is sets off as the most promising substance for mid- and far-IR range application from other materials.

Cadmium-germanium diarsenide, the structural analogue of gallium arsenide GaAs, is one of the most well-known triple diamond-like semiconductor, which differ from GaAs by the high anisotropy of physical properties. CdGeAs2 single crystals are transparent in the spectral range 2.3ё17 m, have the unique coefficient of non-linear susceptibility (d36 = 236 pm/V) and giant non-linear figure-of-merit (d2/n3 = 1288 pm2/V2) [1] among the known non-linear optical materials. Rebirth of interest to this material is caused by the unique possibility its application in high-efficiency transducers of laser radiation on mid- and far-IR range [2]. But the practical application of this material is retarded by the relatively high absorption level in the transparency region. So, the absorption coefficient is 0.2 (CO2-laser frequency) at 300 K. At cooling to 77 K the absorption coefficient decreases in 3 times [3].

Earlier performed studies showed that the situation can be drastically improved if the n-type crystals, grown at low temperatures from non-stoichiometric solution-melt will be used instead of p-type crystals, which usually form from near-stoichiometric CdGeAs2 melts.

Complication of chemical composition of triple semiconductor-based materials has the reasonable limits, especially if components of material have the different volatility and, already for binary semiconductor the uncontrolled temperature fluctuation can vary irreversible its state and properties.

From other side, the directed variation of non-stoichiometry, i.e. the directed variation of composition at the same structure of semiconductor, allows the pronounced improvement of electrophysical characteristics of materials.

So, to control the composition of binary crystal with volatilizable components it is necessary to know p-T-x diagram (where p is the pressure, T – temperature and x – composition). Experimental p-T-x diagram contains the information about the equilibrium compositions of crystal, liquid and gaseous phases in the binary system at determined pressure and temperature and permits to select the conditions and regimes of semiconducting phase growth from melt as well from vapor (if both components are volatilizable).

Complication of atomic composition of crystal at the addition of third component leads to the necessity to study p-T-x-y diagram, where y is the second independent composition coordinate. Meantime, the possibility to growth the different conductivity type crystals can be the reason of dramatic development in the growth technique which associated with the non-stoichiometry of CdGeAs2.

Preliminary physic-chemical study using the method of static tensiometry with Bourdon-type spoon-like quartz gauge showed that CdGeAs2-based crystal phase has the pronounced non-stoichiometry (homogeneity range). One can effects on non-stoichiometry not only by the variation of components concentration in the melt, but also by the variation of arsenic and cadmium partial pressure in gaseous (vapor) phase over the crystals.

Project goal is the elaboration of new technology of nonlinear cadmium-germanium diarsenide crystal growth from non-stoichiometric solution–melt, which allows to produce the pilot samples with sufficiently higher non-linear optical properties in comparison with known materials.

A large amount of nonlinear crystals which dispersion of refractive index will allow its application to realize different parametrical processes are known to date.

Actually, gallium selenide (GeSe), silver selenogallate (AgGaSe2) and zinc germanium phosphide (ZnGeP2) and cadmium-germanium diarsenide (CdGeAs2) are used in the setups of total and difference frequency mixing, as well as in the parametric light generators.

Cadmium-germanium diarsenide is sets off as the most promising substance for mid- and far-IR range application from other materials.

Cadmium-germanium diarsenide, the structural analogue of gallium arsenide GaAs, is one of the most well-known triple diamond-like semiconductor, which differ from GaAs by the high anisotropy of physical properties. CdGeAs2 single crystals are transparent in the spectral range 2.317 m, have the unique coefficient of non-linear susceptibility (d36 = 236 pm/V) and giant non-linear figure-of-merit (d2/n3 = 1288 pm2/V2) [1] among the known non-linear optical materials. Rebirth of interest to this material is caused by the unique possibility its application in high-efficiency transducers of laser radiation on mid- and far-IR range [2]. But the practical application of this material is retarded by the relatively high absorption level in the transparency region. So, the absorption coefficient is 0.2 (CO2-laser frequency) at 300 K. At cooling to 77 K the absorption coefficient decreases in 3 times [3].

Earlier performed studies showed that the situation can be drastically improved if the n-type crystals, grown at low temperatures from non-stoichiometric solution-melt will be used instead of p-type crystals, which usually form from near-stoichiometric CdGeAs2 melts.

Complication of chemical composition of triple semiconductor-based materials has the reasonable limits, especially if components of material have the different volatility and, already for binary semiconductor the uncontrolled temperature fluctuation can vary irreversible its state and properties.

From other side, the directed variation of non-stoichiometry, i.e. the directed variation of composition at the same structure of semiconductor, allows the pronounced improvement of electrophysical characteristics of materials.

So, to control the composition of binary crystal with volatilizable components it is necessary to know p-T-x diagram (where p is the pressure, T – temperature and x – composition). Experimental p-T-x diagram contains the information about the equilibrium compositions of crystal, liquid and gaseous phases in the binary system at determined pressure and temperature and permits to select the conditions and regimes of semiconducting phase growth from melt as well from vapor (if both components are volatilizable).

Complication of atomic composition of crystal at the addition of third component leads to the necessity to study p-T-x-y diagram, where y is the second independent composition coordinate. Meantime, the possibility to growth the different conductivity type crystals can be the reason of dramatic development in the growth technique which associated with the non-stoichiometry of CdGeAs2.

Preliminary physic-chemical study using the method of static tensimetry with Bourdon-type spoon-like quartz gauge showed that CdGeAs2-based crystal phase has the pronounced non-stoichiometry (homogeneity range). One can effects on non-stoichiometry not only by the variation of components concentration in the melt, but also by the variation of arsenic and cadmium partial pressure in gaseous (vapor) phase over the crystals.

Search of correct and comprehensive data, which are beneficial to growth of CdGeAs2 crystals with the best properties, directly connected with the study of p-T-x-y phase diagram of Cd-Ge-As system. It is especially important as well as the system is favourable to formation of metastable states, while measured in the unlimited time static pressure makes it possible to differ stable states from metastable ones.

So, the development of technology of high optical properties CdGeAs2 single crystals growth allows to produce the profitable elements for powerful light sources of mid- and far-IR range. The experience in the study of semiconductor systems and crystal growth gained in IGIC RAS, coupled with the experience in study of ophysicooptical properties of crystals and realizing the different nonlinear-optical devices allows to solve successfully the problem formulated.

New nonlinear crystals for second harmonic generation and frequency mixing of laser radiation, differ from now available by the higher anisotropy and optical transparency (in accordance with the preliminary assessments the absorption can be decreased in order) will be obtained as the result of project realization.

In authors opinion the Project is in the line with ISTC goals of the support of applied studies directed on the producing the elements of different optical devices, in particular devices of environmental and safety control. Powerful modulated sources of light impulses of mid- and far-IR range are namely these pices.

Reference:

1. F.K. Hopkins. Nonlinear materials extend the range of high-power lasers. Laser Focus World, 1995, v.31, No.7, p.87-93.


2. P. Shunemann. Nonlinear crystals provide high power for the mid-IR. Laser Focus World, 1999, v.35, No.4, p.85-89.
3. Yu.M. Andreev, V.G. Voevodin, A.I. Gribenyukov, et al. Second harmonic generation of CO2-laser in CdGeAs2. Optics of atmosphere, 1988, v.1, No.2, p.103-105.


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