RESUMO
Based on a digital micromirror device (DMD) processor as the multi-wavelength narrow-band tunable filter, we demonstrate a multi-port tunable fiber laser through experiments. The key property of this laser is that any lasing wavelength channel from any arbitrary output port can be switched independently over the whole C-band, which is only driven by single DMD chip flexibly. All outputs display an excellent tuning capacity and high consistency in the whole C-band with a 0.02 nm linewidth, 0.055 nm wavelength tuning step, and side-mode suppression ratio greater than 60 dB. Due to the automatic power control and polarization design, the power uniformity of output lasers is less than 0.008 dB and the wavelength fluctuation is below 0.02 nm within 2 h at room temperature.
RESUMO
A digital micromirror device (DMD) is a kind of widely used spatial light modulator. We apply DMD as wavelength selector in tunable fiber lasers. Based on the two-dimensional diffraction theory, the diffraction of DMD and its effect on properties of fiber laser parameters are analyzed in detail. The theoretical results show that the diffraction efficiency is strongly dependent upon the angle of incident light and the pixel spacing of DMD. Compared with the other models of DMDs, the 0.55 in. DMD grating is an approximate blazed state in our configuration, which makes most of the diffracted radiation concentrated into one order. It is therefore a better choice to improve the stability and reliability of tunable fiber laser systems.
RESUMO
The fundamental principle of light modulation is presented. The characteristic of light modulator is discussed both in time and frequency domains. Fourier transform spectrum of the intensity shows that the intensity distribution of outgoing light is the superposition of a series of Dirac functions in the frequency domain. The corresponding intensity distribution curves are also presented. A novel method for phase retardation measurement based on modulated polarized light is introduced. The spectrum analysis indicates that the perfect compensation condition can be satisfied only when the odd frequency components disappear. Under this condition, the phase retardation to be detected can be directly obtained from the compensation quantity of the compensator. This method is a direct measurement which is clearly superior to those indirect methods, especially in terms of high accuracy and low error. Based on the theoretical analysis, relevant experiments were conducted. And experimental results with high precision were obtained.
