Diode Lasers (620 – 680 nm, 808 – 990 nm)

Diode lasers are widely used for measurement applications, as alignment lasers, for pumping of solid-state lasers and for direct material processing. Diode lasers do not require external resonator optics and are mostly coupled to fibers. Many applications require high quality beam steering optics such as beam combiners or scanning mirrors which are shown on the following pages. For more information on pump mirrors for solid-state lasers and combiners for diode lasers please see also pages High Power Lasers on the Basis of Yb- and Nd-doped Materials (1020 – 1080 nm) and .

Turning Mirrors

Fig.1:Reflectance spectra of a broadband turning mirror which can be used for all diode lasers between 808 nm and 980 nm
(AOI = 45°, s- and p-polarization)

Scanning Mirrors

Fig.2:Reflectance spectra of a scanning mirror for diode lasers between 805 and 940 nm combined with R > 50 % between 630 and 670 nm (alignment laser): HRu (22° – 58°, 805 – 940 nm) > 99.3 % + Ru (22° – 58°, 630 – 670 nm) > 50 %

a)Wavelength range of the alignment laser (630 – 670 nm)

b)Wavelength range of the high power diode laser (808 – 980 nm)

Scanning mirrors with other specifications on request
For more information and examples about scanning mirrors please see pages Broadband and Scanning Mirrors (300 – 2500 nm) and Front Surface Silver Mirrors (400 – 4000 nm).

Thin Film Polarizers

Fig.3:Reflectance spectra of a thin film polarizer for 940 nm, AOI = 55°

Fig.4:Reflectance spectra of a broadband thin film polarizer
for 940 – 970 nm:
HRs (45°, 940 – 970 nm) > 99.9 %
+ Rp (45°, 940 – 970 nm) < 1 %

Thin film polarizers are especially useful for polarization coupling of high power laser diodes
For high power 940 nm radiation we recommend to use SUPRASIL 300^®, SUPRASIL 3001/3002^® or Corning 7979^® as substrate material because standard Fused Silica shows an absorption band around this wavelength (see page Fused Silica to Yttrium Aluminum Garnet)

Conventional Steep Edge Combiners for Diode Lasers

Fig.5:Transmittance spectra of conventional steep edge filters HR (980 nm) > 99.9 % + R (915 nm) < 5 % which are used as combiners for pump laser diodes at 915 nm and 980 nm:

a)HRs,p (22.5°, 980 nm) > 99.9 % + Rs,p (22.5°, 915 nm) < 2 %

b)HRs,p (45°, 980 nm) > 99.9 % + Rp (45°, 915 nm) < 2 %

At AOI = 22.5° the conventional steep edge filter separates 915 nm and 980 nm for p-, s-, and unpolarized light
To preserve the steep edge at AOI = 45° the radiation must be polarized and only one polarization can be used. For unpolarized light the slope of the edge can change significantly.

Special Steep Edge Combiners for Unpolarized Light

Fig.6:Transmittance spectra of a special steep edge filter
HRu (45°, 980 nm) > 99.8 % + Ru (45°, 940 nm) < 3 %

Filters of this type can be used as separators or combiners for s- and p-polarized light even at 45° incidence
The cut-on/cut-off edges for the two polarizations only show a spectral separation of about 10 nm
Consequently, these filters can be applied as combiners for unpolarized light of 940 nm and 980 nm diodes at AOI = 45°