A VIPA-based spectrograph with ultra-high resolution and wide band was designed and built by the astronomical photonics team in NIAOT. The fiber-fed spectrograph is compact (W × D × H: 350 mm × 350 mm × 150 mm) and designed to operate without temperature control measures. The spectrograph also provides a fast and accurate measurement of linewidths. Here we report the performances of the VIPA spectrograph, such as the spectral resolution and coverage, the precision of linewidth measurements, the stability with ambient temperature and data acquisition rate, etc.
In recent years, astronomical observation has put forward higher requirements for observation environment, resolution power and simultaneous observation quantity, which makes the cost of traditional spectrometer spiraling. The development of integrated photonics provides a miniaturized, low-cost and environment-friendly solution for astronomical spectral observation. However, high resolution spectrum is hard to achieve because of the highly repetitive structure and defocus aberration existing in re-imaging system when needing cross dispersion. Based on Silica-on-Silicon material platform with a refractive index contrast of 0.23%, new structure of cascaded modulation arrayed waveguides(CMAW) with total length difference of 22mm are arranged in a square chip with a side length of 40mm, having a theoretical resolution of 20,000@1550nm and tested resolution of 15,000@1550nm. Our work demonstrates the potential of integrated photonics applying in high resolution astronomical spectral observation, three times above the record of available resolution power international, which is expected to provide a solution for space observation and large-scale spectral survey.
High-resolution telescopic imaging is very important in astronomy. Super-resolution technology which breaks the diffraction limit of the imaging system can enhance the spatial resolution with compact setup and low cost. In this work, a novel super-resolution telescopic imaging method based on aperture modulation is proposed, and two different algorithms based on intensity extrapolation and image reconstruction for the recovery of super-resolution image are demonstrated respectively. With the help of aperture modulation, redundant information which contains high frequency components beyond the cut-off frequency of the imaging system is coded into the image sequence, and then they are extracted and used to reconstruct the super-resolution image by subsequent signal processing. Experimental results showed that the resolution was enhanced by 2.1 times for extended targets, and 3 times for point sources. Better performance is possible with the improvement of algorithm.
Simultaneous two-color subtraction microscopy using mode multiplexing is realized experimentally. The samples are irradiated with single laser diode at wavelength of 445 nm. Then the beam split laser spots generate separate solid and donut spatial modes and are multiplexed with modulators for simultaneous excitation. The produced fluorescence signals are back collected and further divided into two color bands with dichroic mirrors. Then they are detected with two photomultipliers and demultiplexed in four lock-in amplifiers. Four fluorescence images are recorded in every scan and resolution enhanced images are obtained in two color channels after applying the subtraction strategy. With this method, imaging results of microspheres stained with organic dyes and mesenteric lymph nodes of a mouse labeled with quantum dots (Q525/650) are realized. Improvement of 20% ~ 30% in resolving power of the two color channels compared with confocal microscopy is achieved in with corresponding subtraction factor of about 0.3.
Diode-pumped soliton and non-soliton mode-locked Yb:(Gd1-xYx) 2SiO5 (x=0.5) lasers have been demonstrated together
for the first time to the author's knowledge. For the non-soliton mode locking, output power could achieve ~1.2 W, and
pulse width was about 20ps. For the soliton mode-locked operation, the pulse width was 1.4ps at the wavelength of
1056nm and 375fs at the wavelength of 1042nm, with a pair of SF10 prisms as the negative dispersion elements. The
repetition rate was 48 MHz. The critical pulse energy in the soliton-mode locked operation against the Q-switched mode
locking was much lower than the value in non-soliton mode-locked operation.
We reports on a diode-pumped passively mode-locked Yb:SSO laser with a SESAM. Pulses
duration as short as ~2 ps with a repetition rate of 53 MHz were generated. The output power
achieved ~1.9 W at a pump power of 11.5 W.
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