Calcium lithium niobium gallium garnet crystals activated with Cr³⁺, Tm³⁺, and Ho³⁺ions as a new active medium for λ ≈ 2 μm lasers

Abstract

A novel design of an Earth field digital fluxgate magnetometer is presented, the small magnetometer in low-mass experiment (SMILE). The combination of a number of new techniques results in significant miniaturization of both sensor and electronics. The design uses a sensor with volume compensation, combining three dual rod cores in a Macor R cube with the side dimension of 20 mm. Use of volume compensation provides high geometrical stability of the axes and improved performance compared to component compensated sensors. The sensor is operated at an excitation frequency of 8 kHz. Most of the instrument functionality is combined in a digital signal processing core, implemented in a field programmable gate array (FPGA). The pick-up signal is digitized after amplification and filtering, and values of compensation currents for each of the axes are determined by a digital correlation algorithm, equivalent to a matched filter, and are fed to a hybrid pulse-width modulation/delta-sigma digital-to-analogue converter driving the currents through the compensation coils. Using digital design makes the instrument very flexible, reduces power consumption and opens possibilities for the customization of the operation modes. The current implementation of the design is based on commercial off-the-shelf components. A calibration of the SMILE instrument was carried out at the Nurmijärvi Geophysical Observatory, showing high linearity (within 6 nT on the whole ±50 µT scale), good orthogonality (22 arcmin) and very good temperature stability of the axes.

Na Modification of Lanthanide Doped Ca3Nb1.5Ga3.5O12-Type Laser Garnets: Czochralski Crystal Growth and Characterization

“…Laser operation of CNGG crystals was first studied in flash lamp pumped optical cavities when codoped with Cr 3+ (as activator) and Nd, Tm, Ho, or Er . Similarly, laser properties were also found for the isostructural Ca 3 (Ta 1.5 Ga 0.5 )­Ga 3 O 12 , CTGG, crystal as well as for Li modifications of the two crystals above, i.e., CLNGG and CLTGG.…”

“…This particular feature broadens all Stark−Stark transitions between 2S+1 L J multiplets of the Ln and induces glass-like optical absorption and fluorescence, which has been well documented in Nd:CNGG single crystals. 5,6 Laser operation of CNGG crystals was first studied in flash lamp pumped optical cavities when codoped with Cr 3+ (as activator) and Nd, 7 Tm, 8 Ho, 9 or Er. 10 Similarly, laser properties were also found for the isostructural Ca 3 (Ta 1.5 Ga 0.5 )-Ga 3 O 12 , CTGG, crystal as well as for Li modifications of the two crystals above, i.e., CLNGG and CLTGG.…”