Xia Hou

Conductively cooled all-solid-state zigzag slab laser

A diode pumped, Q-switched Nd:YAG zigzag slab laser is developed using passive conduction cooling. Flat-flat and unstable resonators are adopted in this experiment. The 150-mJ multi-mode and 100-mJ single-mode laser outputs with pulse width of 10 ns are achieved, corresponding to optical efficiencies of 19% and 13%, respectively. The experimental result demonstrates that the laser has the property of compact structure, high efficiency, reliability, and high beam quality. The design of laser has a potential application in space environment.

Diode-side-pumped AO Q-switched Tm,Ho:LuLF laser

A diode-side-pumped Tm,Ho:LuLiF laser at 2-1m wavelength obtained in a ring resonator and its amplification experiment are reported. At the maximum pump energy of 4.7 J available for the oscillator, the output energy per pulse for the oscillator decreases from 904 to 483 mJ in free running mode, and decreases from 106 to 68 mJ in Q-switched mode, with an increase of pump pulse repetition rate from 1 to 5 Hz. When considering the amplifier, 99-mJ Q-switched output energy is achieved at 5-Hz repetition rate.

High-energy nanosecond all-fiber Yb-doped amplifier

We demonstrate a high-energy, low-repetition-rate, all-fiber, 1 064-nm Yb-doped fiber laser based on the master oscillator power amplifier structure. Pulse-pumping technology is used to suppress amplified spontaneous emission. A maximum output pulse energy of 5.97 mJ is obtained at 16-ns pulses with an M2 of 2.9.

In-orbit operation of an atomic clock based on laser-cooled 87 Rb atoms

Atomic clocks based on laser-cooled atoms are widely used as primary frequency standards. Deploying such cold atom clocks (CACs) in space is foreseen to have many applications. Here we present tests of a CAC operating in space. In orbital microgravity, the atoms are cooled, trapped, launched, and finally detected after being interrogated by a microwave field using the Ramsey method. Perturbing influences from the orbital environment on the atoms such as varying magnetic fields and the passage of the spacecraft through Earth’s radiation belt are also controlled and mitigated. With appropriate parameters settings, closed-loop locking of the CAC is realized in orbit and an estimated short-term frequency stability close to 3.0 × 10−13τ−1/2 has been attained. The demonstration of the long-term operation of cold atom clock in orbit opens possibility on the applications of space-based cold atom sensors.Cold atom clocks are among the most precise measuring devices and play key roles in everyday life and scientific explorations. Here the authors demonstrate the first in-orbit atomic clock using cold Rb atoms operating in microgravity and opening possibilities of space surveys and tests of fundamental physics.

Pulsed ytterbium-doped all fiber amplifier near 1μm

An all-fiber master oscillator power amplifier (MOPA) structured pulsed ytterbium (Yb)-doped fiber amplifier is reported in this paper. This amplifier utilizes a single seed diode, which is current-driven to generate optical pulses. The pulses repetition rate is tunable by changing the driven signal repetition rate. The seed pulses are then amplified in a series of Yb-doped fiber amplifiers (YDFAs). The Yb-doped fiber has a large range of fluorescence spectra near 1μm. The cross section of Yb-doped fiber show that input signals ranging from 1000 nm to more than 1100 nm can be amplified in this kind of fiber. This provides a large range of wavelength for amplification. The gain characteristics of Yb-doped fiber amplifier were analyzed. The output pulse shape during the signal amplification was also studied. In order to prove the ability of Yb-doped fibers amplification, we can then perform actual experiments by changing the seed diodes which operating at different wavelength. Here we choose 1030 nm (near an absorption peak of Yb-doped fiber) and 1064 nm (a common wavelength of laser) as the seed wavelength for amplification. The results of the experiment show that both these two wavelength operate well in Yb-doped MOPA structured fiber laser. From the spectrum of the amplified output laser, we can see that the amplified spontaneous emission (ASE) noise is 40 dB lower than the laser signal peak. When the pulses repetition rate is 50 kHz, the final Double-clad Yb-doped fiber achieves a peak power of 14.4 kW without invoking deleterious nonlinear effects.

LD side-pumped Tm,Ho:LuLf pulse laser

An acousto-optical (AO) Q-swithed Tm,Ho:LuLiF laser at 2 µm range has been obtained in a ring resonator by three LDAs side-pumped. The laser energy is 30 mJ per pulse with the pulse width of 417ns.