Spectral Responses And Dispersion Properties Of Chirped Volume Bragg Gratings

Chirped volume Bragg gratings which own designable high efficiency spectral responseand great dispersion, show a wide application during ultrashort pulses’ stretching andcompression. The photo-thermo-refractive glass based chirped volume Bragg grating has apretty high laser damage threshold which is about10J/cm2(with central wavelength of about1064nm), and the maximun dispersion for every centimeter is up to100ps/nm. Thesecharacters could be employed to design a simpler and more efficient ultrashort pulses’compression system. So the study on the characters of chirped volume Bragg gratings makesgreat sense.In the thesis, a semi-analytical theory is studied, which is based on the coupled wavetheory and fundamental matrix approach. Such semi-analytical theory makes the physics ofchirped volume Bragg gratings clear. Each part with different wavelength diffracts at differentdepth of the grating, so the chirped volume Bragg gratings show a wide-band gate-likespectral response and linear group delay. With the increase of the grating thickness and therefractive index modulation, the diffraction efficiency of chirped volume Bragg grating arisesmonotonically. The dispersion depends on the longitudinal chirp rate. The transform matrixmethod is another semi-numerical theory which is applied to prove the semi-analytical theoryand study the spectral responses and dispersion properties of chirped volume Bragg gratingsat different incident angles. The simulation demonstrates that the diffraction curve and thelinear part of group delay move towards the short wavelength as the incident angle increases.The chirped volume Bragg grating based ultrashort pulses’ stretching and compression isstudied numerically. It shows that effective stretching and compression need diffractionefficiency of~100%and wide response bandwidth with more than three times of theultrashort pulses’. For a single chirped volume Bragg grating with thickness of about fewmillimeters to several centimeters, the most available compression is from hundreds ofpicoseconds to several femtoseconds.