Premium and super-polished substrates

For low loss applications like laser gyroscope or resonators with the highest finesse you need mirrors with lowest scattering. Besides using the optimum coating technique (IBS) the choice of the substrates becomes more important, too.

All our substrates as listed on the web pages have a high quality but for the named applications you need substrates with a superior polishing quality, in particular with the lowest possible roughness and surface form errors.

Total back scattering TSB of a mirror, calculated for several surface roughness

Same coating on substrates with different surface roughness

The diagram shows how the scattering will increase due to increasing surface roughness, depending on the wavelength used. A standard polished surface will have a roughness of about 0.5 nm (RMS).

At 532 nm the differences are visible with the naked eye. The substrates in the picture are coated in the same run but have different amounts of surface roughness. The right optic uses a standard substrate (Rq = 0.5 nm), the left one a super-polished one (Rq < 0.1nm).

As you can see, the scattering on the super-po­lished substrate is significantly reduced.

To ensure the lowest possible scattering for our IBS coatings LASEROPTIK offers two classes of substrates with optimized roughness:
Premium: Rq < 0.2 nm
Super-polished: Rq < 0.1 nm

The measured roughness value does of course depend on the technical set-up of the device, like the magnification or field of view. For a better comparison LASEROPTIK specifies the scan length, for the following items the RMS-roughness Rq is measured with 0.3 µm – 1 mm (resolution – scan length).

Premium (Rq < 0.2 nm)


Radius
UV-FS
Ø 12.7 x 6.35 mm
Article-No.

Stock
UV-FS
Ø 25 x 6.35 mm
Article-No.

Stock
plano S-08458 S-08457  
–30 mm S-08449  
–50 mm S-08444  
–100 mm S-08442  
–150 mm S-08447  
–200 mm S-08443  
–250 mm S-08451  
–300 mm S-08448 S-08454
–400 mm S-08446 S-08453
–500 mm S-08441 S-08456
–1000 mm S-08450 S-08455
–1500 mm S-09959   S-08452
–2000 mm S-08445 S-09960  

 available from stock

Super-polished (Rq < 0.1 nm)


Radius
UV-FS
Ø 12.7 x 6.35 mm
Article-No.

Stock
UV-FS
Ø 25 x 6.35 mm
Article-No.

Stock
plano S-09965 S-09966  
–500 mm S-09961 S-09962  
–1000 mm S-09963   S-09964

 available from stock

Quality can be inspected by our inhouse test equipment (for more information see Measuring methods):

Optical profiler (Zygo NewView 9000)

Automated roughness testing

Laser testing lab