Measurement of thermal effect in laser pumped silicon employing infrared digital holographic interferometry

We present a short-coherence infrared digital holographic interferometry (IRDHI) to quantitatively measure the weak thermal effect in silicon wafer under visible laser pumping. In IRDHI, a superluminescent diode and a narrow-band filter are introduced to eliminate the self-interference fringes and suppress the noise. The effect of coherence length of the detection light source is analyzed and the optimal coherence length range in the proposed configuration is given. Meanwhile, we measure the weak thermal effect in silicon pumped by two different approaches of a continuous visible laser with different powers. The proposed configuration, which shows high stability and sensitivity, can be easily adapted and improved to measure the variation of thermal effect or refractive index in other near infrared transparent materials.