Optics for Ultrafast Lasers in the Wavelength Range of 1000 – 1600 nm

Although Ti:Sapphire lasers are currently the most important ultrafast lasers, many applications require ultrafast pulses at considerably longer wavelengths. Several lasers emitting light between 1100 nm and 1600 nm have been developed, such as the Cr:Forsterite laser (1150 – 1350 nm) or the Er:Fiber laser (1550 nm). Some examples of coatings such as negative dispersion mirrors and mirror pairs for these wavelength ranges are presented.

Optics for Ultrafast Lasers in the Wavelength Range of 1000 – 1600 nm

Special Features

Very high reflectance of the mirrors
(R > 99.8 % … R > 99.99 % depending on the design)
Center wavelength, bandwidth, GDD and TOD according to customer specifications
Spectral tolerance ±1 %
In-house design calculation and measurement capabilities (GDD 250 – 1700 nm, reflectance 210 – 1800 nm)

Negative Dispersion Laser and Pump Mirrors for AOI = 0°

Fig.1:Reflectance and GDD spectra of a negative dispersion laser mirror (GDD ≈ -60 fs² for 1200 – 1370 nm)

a)Reflectance vs. wavelength

b)GDD vs. wavelength

Fig.2:Reflectance and GDD spectra of a negative dispersion pump mirror:
HR (0°, 1180 – 1380 nm) > 99.8 % + R (0°, 1020 – 1070 nm) < 5 %,
GDD-R (0°, 1180 – 1380 nm) ≈ -150 fs²

a)Reflectance vs. wavelength

b)GDD vs. wavelength

GTI-Mirrors for AOI = 0°

Fig.3:Reflectance and GDD spectra of GTI mirrors for 1500 nm with different GDD values

a)Reflectance vs. wavelength

b)GDD vs. wavelength

Broadband Negative Dispersion Mirror Pairs for AOI = 0°

Fig.4:Reflectance and GDD spectra of a broadband negative dispersion mirror pair; single mirrors with R > 99.7 % (mirror A) and R > 99.85 % (mirror B)

a)Reflectance vs. wavelength

b)GDD vs. wavelength

Specially designed mirror pairs show a very smooth average GDD spectrum, although the single broadband mirrors exhibit strong GDD oscillations. Pump mirror pairs (i.e. mirror pairs with one mirror showing high transmittance at the pump wavelength of the respective laser type) are also available.

Broadband Negative Dispersion Turning Mirrors for AOI = 45°

Fig.5:Reflectance and GDD spectra of a broadband negative dispersion mirrors

a)Reflectance vs. wavelength

b)GDD vs. wavelength

Please note the large bandwidth of this mirror. In contrast, low dispersion turning mirrors are available with bandwidths of about 200 nm for p-polarization and about 400 nm for s-polarization in this wavelength range.

Fig.6:Reflectance and GDD spectra of a beam combiner:
HRs (45°, 1100 – 1700 nm) > 99.5 % + Rp (45°, 450 – 900 nm) < 15% (average Rp < 10 %)
|GDD-Rs (45°,1100 – 1700 nm)| < 750 fs² + |GDD-Tp (45°,450 – 950 nm)| < 300 fs²

a)Reflectance p-pol. vs. wavelength

b)Reflectance s-pol. vs. wavelength

c)GDD-Tp (45°) vs. wavelength

d)GDD-Rs (45°) vs. wavelength

Optics for Ultrafast Lasers in the Wavelength Range of 1000 – 1600 nm