We demonstrate laser cooling of trapped beryllium ions at 313 nm using a frequency-doubled extended cavity diode laser operated at 626 nm, obtained by cooling a ridge waveguide diode laser chip to -31°C. Up to 32 mW of narrowband 626 nm laser radiation is obtained. After passage through an optical isolator and beam shaping optics, 14 mW of 626 nm power remains of which 70% is coupled into an external enhancement cavity containing a nonlinear crystal for second-harmonic generation. We produce up to 35 μW of 313 nm radiation, which is subsequently used to laser cool and detect 6×10(2) beryllium ions, stored in a linear Paul trap, to a temperature of about 10 mK, as evidenced by the formation of Coulomb crystals. Our setup offers a simple and affordable alternative for Doppler cooling, optical pumping, and detection to presently used laser systems.
We demonstrate two systems based on vertical-external-cavity surface-emitting lasers (VECSELs) for producing ultraviolet laser light at wavelengths of 235 and 313 nm. The systems are suitable for quantum information processing with trapped beryllium ions. Each system consists of a compact, single-frequency, continuous-wave VECSEL producing high-power near-infrared light, tunable over tens of nanometers. One system generates 2.4 W at 940 nm, using a gain mirror based on GaInAs/GaAs quantum wells, which is converted to 54 mW of 235 nm light for photoionization of neutral beryllium atoms. The other system uses a gain mirror based on GaInNAs/GaAs quantum wells, enabling wavelength extension above 1200 nm with manageable strain in the GaAs lattice. This system generates 1.6 W at 1252 nm, which is converted to 41 mW of 313 nm light that is used to laser cool trapped 9Be+ ions and quantum state preparation and detection. The 313 nm system is also suitable for implementing high-fidelity quantum gates.
Experiments in atomic, molecular, and optical (AMO) physics rely on lasers at many different wavelengths and with varying requirements on spectral linewidth, power, and intensity stability. Vertical external-cavity surface-emitting lasers (VECSELs), when combined with nonlinear frequency conversion, can potentially replace many of the laser systems currently in use. Here we present and characterize VECSEL systems that can perform all laser-based tasks for quantum information processing experiments with trapped magnesium ions. For photoionization of neutral magnesium, 570.6
nm light is generated with an intracavity frequency-doubled VECSEL containing a lithium triborate (LBO) crystal for second harmonic generation. External frequency doubling produces 285.3
nm light for resonant interaction with the
1S0↔ 1P1 transition of neutral Mg. Using an externally frequency-quadrupled VECSEL, we implement Doppler cooling of
25Mg
+ on the 279.6
nm
2S1/2↔ 2P3/2 cycling transition, repumping on the 280.4
nm
2S1/2↔ 2P1/2 transition, coherent state manipulation, and resolved sideband cooling close to the motional ground state. Our systems serve as prototypes for applications in AMO requiring single-frequency, power-scalable laser sources at multiple wavelengths.
We have developed a semiconductor laser system used in 40K-87Rb trapping and cooling experiment. The laser diode system is composed of three external cavity diode lasers and four injection diode lasers and a tapered amplifier. Four laser beams used for 40K and 87Rb cooling and repump lights are obtained by using acoustic optic modulators to offset the frequencies from the three external cavity diode lasers. Four light beams with different frequencies are injected into four slave lasers for injection locking. Then Rb cooling light, K cooling light and K repump light are injected into a semiconductor tapered amplifier in a master oscillator-power configuration. This configuration is flexible and stable and can simultaneously produce the cooling and repump light for 40K and 87Rb trapping and cooling experiment.
A laser system for Doppler cooling of ytterbium ion on the transition in a single-ion optical frequency standard is developed. The second harmonic of a semiconductor laser with a wavelength of is used for cooling. The laser frequency is doubled in a nonlinear BiBO crystal embedded in a ring resonator, which also serves as a reference for laser frequency stabilisation. Second-harmonic power of is generated at a wavelength of . Diode laser radiation is modulated by an electro-optic modulator at to generate a sideband exciting the hyperfine component of the cooling transition that is not excited by resonant cooling light. The sideband relative intensity of a few percent proved to be sufficient to reduce the ion dwelling time in the state to less than and increase the cooling efficiency.