UBC Undergraduate Research

Wavelength tunable femtosecond fiber laser : results and recommendations Pa, Jack; Young, Robert


The research objective of this project is to construct and characterize a wavelength tunable fiber laser. The set up takes advantage of a grating compressor to shorten the width of the generated pulses, and a photonic crystal fiber to shift the output wavelength through the soliton self-frequency shift (SSFS) effect. The quantitative objective is to construct a system that outputs roughly 5mW pulses with wavelengths between 1030 and 1500 nm with pulse widths around 200fs and a pulse rate of 100MHz. To obtain these desired specifications, pulse shaping optics were used to alter the output parameters detailed below. First, a pre amplifier will be used to amplify incoming pulses to the required pulse power. However, since the diode for the pre-amplifier malfunctioned, a laser oscillator with similar parameters was used instead as a temporary replacement. As a result the pre-amplifier could not be fully validated for performance. A grating compressor made up of two transmission gratings will be used to compress the incoming pulses to reach the 200fs range. Finally, the output is then coupled to a photonic crystal fiber (PCF) where the wavelength of the beam is shifted to achieve wavelength tunability. As of the original intended deadline of this report, two of the three major components mentioned in the above paragraph has been completed and fully characterized. The grating compressor has been aligned and adjusted to obtain a confirmed pulse width of approximately 200fs (± 2.6fs) using the autocorrelator device. A minor wavelength peak shift was observed in the two tested fiber ranging from approximately1030 to 1067nm.The pre-amplifier has been completed and currently waiting for a replacement pump diode before having it revalidated. Based on the current status and results, while the pulse shaping optics and fiber coupling apparatus has been completed (some not yet fully characterized), the required tunable wavelength range was not achieved. It is recommended that for future work on the system, the pre-amplifier be completed and used to further increase the incident intensity into the PCF, the core size and length of the PCF to be made smaller and longer respectively to increase the nonlinear effects, and the system be further optimized through alignment to minimize avoidable power losses. The pulse width could also be decreased further to increase the nonlinear effect.

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