[Improvement of grating spectrograph and its application to frequency-doubling in PPLN]

Charge-coupled device (CCD) has been widely used in spectral detection and spectral imaging fields, which has a number of benefits: broad spectral range response, low detection limit, wide dynamic range, minimal dark current and readout noise as well as the abilities of signal integration, simultaneous multichannel detection, and real-time detection. The combination of a traditional one meter grating spectrograph and a science charge-coupled device (CCD) led to a real-time grating spectrograph for laser spectrum detection developed in this paper. Based on the new grating spectrograph, the spectral characteristic of frequency-doubling of a broad band double-cladding fiber laser in polarized lithium niobate (PPLN) has been investigated. Dynamic spectrum of the second harmonic with varying temperature of PPLN has been observed and analyzed in detail.