Materials: Gallium Arsenide

Gallium Arsenide

Semi-insulating GaAs provides an alternative to ZnSe in medium and high-power CW CO2 laser systems for lenses and rear mirrors. GaAs is particularly useful in applications where toughness and durability are important. Its hardness and strength make GaAs a good choice where dust or abrasive particles tend to build up or bombard the optical surface. Softer substrates allow particles to imbed in the optic even when the best coatings are used.

GaAs is manufactured for semiconductor applications rather than optical applications, so careful material screening is vital in producing quality GaAs optics. At II-VI, we utilize our laser vacuum calorimetry capability and other techniques to screen out materials with voids, inclusions, or other defects which cause inferior optical performance.

GaAs optics are limited by crystal growth technology to diameters typically less than 10 cm. The material is non-hygroscopic, safe to use in laboratory and field applications, and chemically stable except when contacted with strong acids.


Material Properties

Optical Properties

Bulk Absorption Coefficient @ 10.6µm

<= 0.01 /cm

Temperature Change of Refractive Index @ 10.6µm

149 x 10-6/°C


Thermal Properties

Thermal Conductivity @ 20° C

0.48 W/cm/°C

Specific Heat

0.325 J/g/°C

Linear Expansion Coefficient @ 20° C

5.7 x 10-6/°C


Mechanical Properties

Young’s Modulus

83 GPa (12.04 x 106 psi)

Rupture Modulus

138 MPa (20,000 psi)

Knoop Hardness

750 kg/mm2

Density

5.37 g/cm3

Poisson’s Ratio

0.31



Wavelength
(µm)

Index

Wavelength
(µm)

Index

Wavelength
(µm)

Index

Wavelength
(µm)

Index

2.6

3.3239

5.4

3.2991

8.2

3.2868

11.0

3.2725

2.8

3.3204

5.6

3.2982

8.4

3.2859

11.2

3.2713

3.0

3.3169

5.8

3.2972

8.6

3.2849

11.4

3.2701

3.2

3.3149

6.0

3.2963

8.8

3.2840

11.6

3.2690

3.4

3.3129

6.2

3.2955

9.0

3.2830

11.8

3.2678

3.6

3.3109

6.4

3.2947

9.2

3.2818

12.0

3.2666

3.8

3.3089

6.6

3.2939

9.4

3.2806

12.2

3.2651

4.0

3.3069

6.8

3.2931

9.6

3.2794

12.4

3.2635

4.2

3.3057

7.0

3.2923

9.8

3.2782

12.6

3.2620

4.4

3.3045

7.2

3.2914

10.0

3.2770

12.8

3.2604

4.6

3.3034

7.4

3.2905

10.2

3.2761

13.0

3.2589

4.8

3.3022

7.6

3.2896

10.4

3.2752

13.2

3.2573

5.0

3.3010

7.8

3.2887

10.6

3.2743

13.4

3.2557

5.2

3.3001

8.0

3.2878

10.8

3.2734

13.6

3.2541