UC Irvine

Dispersive Fourier Transform (DFT) is a measurement technique that facilitates wavelength to time mapping through optical dispersive elements with large and linear group velocity dispersion (GVD) such as dispersive fibers or chirped fiber bragg gratings (CFBG). This technique has been applied to several scientific and industrial applications such as analog to digital converters to increase effective sampling rates, spectroscopy to enable single-shot real-time spectral measurements, optical arbitrary waveform generation, and real time imaging to capture fast dynamic processes.

In this work, Dispersive Fourier Transformation and its application on real time imaging are investigated. We demonstrated a fast dispersive laser scanning system that can achieve horizontal scanning through Raman amplified DFT and diffraction grating system and vertical scanning by employing MEMS based digital micro mirror arrays technology. The proposed technique employs real time dispersive imaging system, which captures spectrally encoded images with a single photodetector at pulse repetition rate via space-to-time mapping technology. Wide area scanning capability is introduced by using individually addressable micro mirror arrays as a beam steering device.

Experimentally, we scanned ∼20mm2 at scan rate of 5kHz with ∼150μm lateral and ∼160μm vertical resolution that can be controlled by using 1024x768 mirror arrays. With the current state of the art MEMS technology, fast scanning up to 32.5kHz scan rate and resolution down to single mirror pitch size of 10.8μm is also achievable. Moreover, we investigated and demonstrated the ideas to improve the system to achieve larger area scan with faster scan rates and higher resolution while optimizing power.