Abstract

Two-photon excited fluorescence (TPEF) has become a standard technique in modern microscopy [1] but it is still affected by photo-damage of the probe owed to high excitation intensities. In this work we report on utilizing the photon bunching effect in thermal light to enhance the efficiency of TPEF under continuous wave excitation. We used a super-luminescence diode (SLD) as thermal light source and compared it to coherent excitation from a DFB diode laser emitting at the same wavelength. The degree of second order coherence g⁽²⁾ of both sources was measured following a scheme described in [2]. The SLD showed photon bunching with g⁽²⁾ = 1.90±0.2 as expected for thermal light, while the DFB diode laser emitted coherent light exhibiting no photon bunching at g⁽²⁾ = 1.

© 2013 IEEE