Diffraction-limited Wavefront Research Articles

Wavefront Analysis of Nonlinear Self-Amplified Spontaneous-Emission Free-Electron Laser Harmonics in the Single-Shot Regime

The single-shot spatial characteristics of the vacuum ultraviolet self-amplified spontaneous emission of a free electron laser (FEL) is measured at different stages of amplification up to saturation with a Hartmann wavefront sensor. We show that the fundamental radiation at 61.5 nm tends towards a single-mode behavior as getting closer to saturation. The measurements are found in good agreement with simulations and theory. A near diffraction limited wavefront was measured. The analysis of Fresnel diffraction through the Hartmann wavefront sensor hole array also provides some further insight for the evaluation of the FEL transverse coherence, of high importance for various applications.

Measurement of the wavefront of a laser diode system for intersatellite communication by a Jamin double-shearing interferometer

The frame of a laser diode transmitter for intersatellite communication is concisely introduced. A simple, novel and visual method for measuring the diffraction-limited wavefront of the transmitter by a Jamin double-shearing interferometer is proposed. To verify the validity of the measurement, the far-field divergence of beam is additionally rigorously analysed in terms of the Fraunhofer diffraction. The measurement, the necessary analyses and discussion are given in detail. By directly measuring the fringe widths and quantitatively interpreting the interference fringes, the minimum detectable wavefront height (DWH) of the wavefront is only 0.2 gimel (the distance between the perfect plane wavefront and the actual wavefront at the transmitting aperture) and the corresponding divergence is only 65.84 mu rad. This indicates that the wavefront approaches the diffraction-limited condition. The results show that this interferometer is a powerful tool for testing the semiconductor laser beam's wavefront, especially the diffraction-limited wavefront.

Jamin double-shearing interferometer for diffraction-limited wave-front test.

A Jamin double-shearing interferometer with three changeable schemes is proposed for the measurement of diffraction-limited laser wave front. A concept of detectable wave-front height is thus defined, and on this basis the limits of detectable wave-front height from the suggested schemes of interferometer are analyzed. The design is detailed, the simulation for wave aberrations is given, and the experiment is demonstrated. One of the major features of this interferometer is that it is capable of visually testing a diffraction-limited wave front immediately by the fringes with the matched accuracy and minimum detectable wave-front height on the order of 0.1lambda.