Rangefinder systems that are built with 1550 nm pulsed laser diodes (PLDs) also operate at high power levels yet still in the eye-safe range – due to their wavelength. Common night-vision goggles cannot detect this wavelength, which makes these PLDs particularly well suited for military laser rangefinders or friend/foe identification.
The base material of the 1550 series is InP with additional InGaAsP layers. The InGaAsP structure ensures high reliability, very good beam characteristics, and a high temperature stability. The wide operating temperature range is between –45°C and +85°C. The 1550 nm pulsed laser diodes are housed in a TO-18 can. They are also available in 9 mm packages or in customer-specific designs.
The stack design of standard diodes yields an output power of about 15-20% above the market average.
- Efficiency: 0.35 W/A
- Peak power: at least 45 W at a pulse length of 150 ns
- Beam divergence: an excellent 12° x 30°
- Output power of a single emitter: 3 W to 12 W
- Output power of stacked emitters: 10 W and 45 W
Even as a single emitter, high intensity PLDs with an efficiency of 0.5 W/A yield a peak power of 35 W at a beam divergence of only 12° x 25°.
Multi-junction laser technology is similar to nanostack technology. One laser diode chip contains several epitactically integrated emitters. The 155G1S2J02x produces an output power of 5 W (@ 150 ns, df= 0.1%) at a strip size of only 50 µm x 7 µm with two emitters. At shorter pulse lengths the optical peak power can be overdriven accordingly.
The Divergence of the fast axis was optimized by the additional assembly of a fast axis collimation (FAC) lens that is attached directly in front of the laser diode chip. Depending on the lens used, divergences of 10 mrad can be achieved. The integration of both the chip and the lens in a small, hermetically sealed TO-46 housing is particularly advantageous. This design withstands acceleration rates of over 1000 g/ms without a problem, as is required for use in military technology.
This technology is also optionally available with 905 nm pulsed laser diodes. If the wavelength has to be controlled exactly, a thermoelectric cooler (TEC) can be integrated into a TO-8 housing.