Solar-pumped laser has attracted attention in the area of renewable energy creation. However, since the conversion efficiency from solar energy to laser energy is low, such lasers are not yet in practical use. In this work, we developed Nd3+,Cr3+ codoped YVO4 and CaYAlO4 crystals for solar-pumped laser. We succeeded to increase absorption at UV-VIS region with both crystals drastically. The absorption cross section of Nd,Cr:CaYAlO4 around 400 nm was more than 70 times that of Nd,Cr:YAG crystals. The fluorescence at 1 μm was observed by pumping at 400 nm. It indicates that energy transfer from Cr to Nd occurred effectively.
Always, in the atmosphere of the earth we live in is a luminous phenomenona (Fluorescence by cosmic rays,
lightning and aurora etc..) has been occurring. JEM-EUSO (Extreme Universe Space Observatory onboard
Japanese Experiment Module) experiment is the observation that aims to capture the luminous phenomenon in
earth's atmosphere from orbit. JEM-EUSO telescope observations have been using a Fresnel lens of the world's
largest. The observation area (250km radius at the sea level) is extremely larger than the telescope installed
on the ground to captures the luminous phenomenon. The main target of EUSO is to capture the fluorescence
emission caused by UHECR (Ultra-High-Energy Cosmic Ray). This way that is extremely large observation area
for UHECR will be frontier for astronomical observation of charged particles for relatively near space (50Mpc).
Because JEM-EUSO observe fluorescence in the atmosphere of the earth from space, it is necessary to measure
the state of the atmosphere (cloud cover and transparency in particular) for the calibration. The infrared camera
mounted on the JEM-EUSO is used to measurement of cloud coverage and cloud top height. For the atmospheric
transparency measurement and calibration of the cloud top height, we use the LIDAR system using EUSO's
telescope and the laser. It is also possible that in addition to this, to know the state of the atmosphere based
on the background light captured by EUSO's telescope. These measurements of atmospheric conditions for the
observation of UHECRs is not only calibration data. The atmospheric observation that covers the entire ground
is the vital information in the geophysical.
Furthermore, it is possible to measure light emission by lightning or meteor that occur in the field of view
during observation of darkness in the JEM-EUSO. Expected by combining a lot of measurement, to understand
of the earth and proceed further.
Laser remote sensing technologies are valuable for a variety of scientific requirements. These measurement techniques
are involved in several earth science areas, including atmospheric chemistry, aerosols and clouds, wind speed and
directions, prediction of pollution, oceanic mixed layer depth, vegetation canopy height (biomass), ice sheet, surface
topography, and others. Much of these measurements have been performed from the ground to aircraft over the past
decades. To improve knowledge of these science areas with transport models (e.g. AGCM), further advances of vertical
profile are required.
JAXA collaborated with NICT and RIKEN started a new cross-sectional 3-year program to improve a technology
readiness of the critical 1-micron wavelengths from 2011. The efficient frequency conversions such as second and third
harmonic generation and optical parametric oscillation/generation are applied. A variety of elements are common issues
to lidar instruments, which includes heat rejection using high thermal conductivity materials, laser diode life time and
reliability, wavelength control, and suppression of contamination control. And the program has invested in several
critical areas including advanced laser transmitter technologies to enable science measurements and improvement of
knowledge for space-based laser diode arrays, Pockels cells, advanced nonlinear wavelength conversion technology for
space-based LIDIRs. Final goal is aim to realize 15 watt class Q-switched pulse laser over 3-year lifetime.
A compact and high-energy pulsed mid-infrared laser using an optical parametric oscillator (OPO) has been developed
using a diode-pumped and Q-switched Tm,Ho:YAG ceramic laser with a wavelength of 2.09 μm as a pump source. A
singly-resonant OPO with a 20 mm long AgGaSe2 crystal was used, and the crystal was set at an angle normal to the
pump beam. The output idler pulse energy was up to about 200 μJ with the pump energy of about 6 mJ for both the type
I and type II phase matching conditions. The wavelength of the idler pulses was 5.97 and 6.37 μm for type I and type II,
respectively. The output characteristics predicted using a model calculation were in good agreement with the
experimental results. It is suggested that the output idler pulse energy in the experiment is limited by the surface damage
threshold of the AgGaSe2 crystal. By increasing the pump beam diameter from 1 to 3 mm (3-fold) and the pump energy
from 6 to 54 mJ (9-fold), the idler pulse energy of 1.8 mJ (= 200 μJ × 9) will be obtained without increasing the pump
intensity and without saturation of the output idler pulse energy.
Since resonant absorption of light caused by a variety of different molecular bond occurs in the mid-infrared (MIR)
wavelength region, many applications using tunable MIR lasers have been reported. However, the applicable fields of
the MIR tunable lasers have been restricted by their large size and high cost equipments. Therefore, we are developing a
compact tunable MIR laser using an optical parametric oscillator (OPO). To obtain a long term stability and a high
conversion efficiency, a diode-pumped and Q-switched Tm,Ho:YAG ceramic laser with a wavelength of 2.1 μm was
adopted for the pump source. A maximum output energy of 40 mJ was obtained with the Tm,Ho:YAG ceramic laser at a
pulse width of 150 ns and a repetition rate of 10 Hz. An experiment was performed using a singly-resonant OPO with a
ZnGeP2 crystal pumped by another OPO with a wavelength of 2.1 μm. A threshold pump fluence of 0.2 J/cm2 and a
slope efficiency of 60% were obtained at a signal and idler wavelengths of 3.3 and 5.6 μm, respectively. Using these
results and a theoretical model calculation, the maximum output energy of MIR-OPO pumped with the Tm,Ho:YAG
ceramic laser was estimated to be about 20 mJ.