http://www.layertec.de/bk7.html
Material data of BK7 Schott glass
 

Transmission Spectrum of BK7
Schott glass windows (3 mm thickness)

 
Refractive index n and internal transmittance ti
Wavelength [nm] n ti (t=5mm)
365 1.53627 0.994
404.7 1.53024 0.998
435.8 1.52668 0.999
480 1.52283 0.999
486.1 1.52238 0.999
546.1 1.51872 0.999
587.6 1.5168 0.999
589.3 1.51673 0.999
632.8 1.51509 0.999
643.8 1.51472 0.999
656.3 1.51432 0.999
706.5 1.51289 0.999
852.1 1.50980 0.999
1014 1.50731 0.999
1060 1.50669 0.999
1529 1.50091 0.997

Applications 

Plane and curved mirror substrates
Windows and spherical lenses
All with any type of coating (HR, PR, AR) for the wavelength range given in the table
All transmittive components are selected to be free of bubbles and inclusions

 

Properties 

High transmission from VIS to NIR
Very good homogeneity

 

Optical Data 

Homogeneity (dn):
Standard: < 2 x10-5
On request: down to 1 x 10-6
Max. bubble diameter: < 0.1 mm
Max. cross section of bubbles in 100 cm³ of glass: < 0.03 mm²
Max. cross section of inclusions in 100 cm³ of glass: < 0.03 mm²

 

Mechanical Data 

Density: 2.51 g/cm³
Young modulus: 82 GPa
Poisson ratio: 0.206

 

Thermal Data 

Thermal linear expansion coefficient
-30...+70°C: 7.1 x 10-6 K-1
+20...+300°C: 8.3 x 10-6 K-1
Specific heat capacity: 858 J/(kgK)
Thermal conductivity: 1.114 W/(mK)
Melting point: 559 °C