Panchromatic InGaAs or Silicon?
At longer wavelengths panchromatic InGaAs has a higher temperature stability than silicon and is thus a viable alternative in laser applications at approximately 1,000 nm.
The sensitivity range of our new InGaAs PIN diodes – IG17, IG22, and IG26 – not only covers the SWIR spectral range but the visible range as well: This characteristic is referred to as “panchromatic.” An example of IG22 is shown in Fig. 1.
In a measurement application, this signal should depend on disturbance factors as little as possible in order to be as independent of the environmental temperature as possible. With silicon, this property exists in wavelengths that are less than 900 nm; the temperature coefficient of the sensitivity is constant at <0.1%/K and can be corrected using software.
The longer the wavelengths are, the faster this dependency increases and the more difficult it becomes to make a software correction.
This effect is particularly disturbing in laser applications at approximately 1,000 nm. Here InGaAs presents a viable alternative to silicon.
The signal loss is marginal. The IG17 series components exhibit a constant temperature coefficient of <0.1%/K at 1,000 nm. According to the tests we ran, the IG22 series is, at a value of approximately 0.002%/K, even more temperature independent and should thus definitely be considered for use. Fig. 2 shows the corresponding spectral behavior of the temperature coefficient.
