A broad-angle spectrum reflection pump–probe technique based on the Brewster angle

Here, a sensitive reflection pump–probe technique is demonstrated for studying the optical nonlinear (NLO) properties of samples with a high linear absorptive coefficient at a certain wavelength. Light with a broad-angle spectrum around the Brewster angle is applied as the incident beam. An adjustable slit is utilized to select a part of the reflection angle, replacing the traditional rotation method in the reflection pump probe. The sensitivity of this technique is affected by the position and width of the slit. The closer to the Brewster angle, the more sensitivity the technique achieves. This technique can precisely control the angle of reflection, resulting in a significant enhancement with easier system operation. In addition, the simple optical path used here can be applied to other techniques for studying the properties of NLO samples. Experimentally, a normalized reflectivity enhancement is observed at 532 nm, and the impact of the incident angle on the pump-probe signal of the silicon crystal is investigated.