We demonstrate a low-concentrated solar-pumped fiber laser with all-inorganic cesium lead halide perovskite quantum dots (QDs), which function as a sensitizer. The perovskite QDs exhibit substantial advantages for solarpumped laser applications because of their broad absorption and narrow emission spectra with high quantum yield. We successfully tuned the peak emission wavelength of the perovskite QDs by altering the I/Br ratio in order to achieve spectral overlap with Nd3+ ions, which have been widely used as a laser medium for solar-pumped lasers. The measurement results show that the laser output power is highly sensitive to the peak emission wavelength of the QDs. Although our synthesized QDs have a quantum yield of approximately 65%, which is less than that of conventional organic dyes, the laser performance was comparable because the fluorescence spectrum is tailored to the Nd3+ absorption band.
In this paper, we demonstrate an extremely low-concentrated solar-pumped laser (SPL) that uses a transversely excited fiber laser geometry. To eliminate the need for precise solar tracking with an aggressive cooling system and to considerably increase the number of laser applications, low-concentration factors in SPLs are highly desired. We investigate the intrinsic low-loss property of SiO2 optical fibers; this property can be used to compensate for the extremely low gain coefficient of the weakly-pumped active medium by sunlight. As part of the experimental setup, a 40-m long Nd3+-doped SiO2 fiber coil was packed in a ring-shaped chamber filled with a sensitizer solution; this solution functioned as a down-shifter. The dichroic top window of the chamber transmitted a wide range of sunlight and reflected the down-shifted photons, confining them to the highly-reflective chamber until they were absorbed by the Nd3+ ions in the active fiber. We demonstrated a lasing threshold that is 10 times the concentration of natural sunlight and two orders of magnitude smaller than that of conventional SPLs.
Output power enhancement of an all gas-phase iodine laser (AGIL) by addition of hydrocarbon gases is studied. It is
expected because hydrocarbon gases might scavenge Cl atoms, which are strong quencher of the upper state of the laser
medium, I(2P1/2). In AGILs, suppression of the Cl atom concentration is the key to improving the efficiency of laser
operation because Cl atoms are inherently generated by the self-annihilation of the energy donor, NCl(a1Δ). We found
that the addition of CH4 gave the best results because of its high scavenging rate constant and inertness to I(2P1/2). An
enhancement of 10% was observed in the output power when CH4 was added at a flow rate twice that of NCl3. On the
other hand, when C2H4 or C2H2 were added at the same flow rate as that of CH4, the output power reduced despite their
fast removal rate of Cl atoms. The reason for the reduced output power was that the unsaturated bonds scavenged not
only the Cl atoms but also the H atoms, resulting in a low density of H atoms, and this decelerated the production of
NCl(a1Δ). The observed laser characteristics could be reasonably explained by numerical model calculations.
The characteristics of an all gas-phase iodine laser (AGIL) that uses molecular iodine as a source of iodine atoms is
studied. The laser is based on the energy transfer reaction between metastable NCl(a1Δ) and ground state I(2P3/2) atoms,
which are produced by the electric discharge of a mixture of I2 and He. At fixed flow rates of the chemical species, the
laser output powers are measured at three different positions in a flow reactor. The output power is characterized by a
function of the optical axis position and is reasonably reproduced by the numerical calculation. A repetitive pulse of laser
output at 50 Hz with a duty factor of 40% is observed. The highest output power is 40 mW at 210 mm downstream from
the mixing point of I/H/He and NCl3. This is 80% of the output power generated from the conventional system using HI
as an iodine donor. The measured results of the time resolved laser output power suggest that the output power of the I2-
AGIL is more sensitive to the electric discharge plasma intensity as compared to that of the HI-AGIL. An AGIL operated
using I2 could potentially have the same output power as that of an AGIL operated using HI if a continuous-wave electric
discharge generator is used.
Theoretical and experimental studies of the amine-based all gas-phase iodine laser (AGIL) are conducted. The numerical
simulation code is a detailed one-dimensional, multiple-leaky-stream-tubes kinetics code combined with all the known
rate equations to date. Using this code, we find that the key reactions to achieve positive gain are the deactivation
reaction of excited iodine atoms by chlorine atoms and the self annihilation reactions of NCl(1Δ). The order of the
injection nozzles is crucial to suppress these reactions. Following the calculations, we fabricate a flow reactor apparatus
and demonstrate laser action for the 2P1/2-2P3/2 transition of iodine atom pumped by energy transfer from NCl(1Δ)
produced by a set of amine-based, all gas-phase chemical reactions. Continuous-wave laser output of 50 mW with 40%
duty factor is obtained from a stable optical resonator consisting of two 99.99% reflective mirrors. The observed laser
characteristics are reasonably explained by numerical calculations. To our knowledge, this is the first achievement of
amine-based AGIL oscillation.
Numerical simulation and flow-tube experiments are conducted to understand the chemistry of an amine-based all gasphase
iodine laser (AGIL). The numerical simulation code developed is a one-dimensional, multiple-leaky-stream-tubes
kinetics code combined with all the known rate equations to date. Using this code, we find that the key reactions to
achieve positive gain are the deactivation reaction of excited iodine atoms by chlorine atoms and the self annihilation
reactions of NCl(1Δ). The order of the injection nozzles is crucial to suppress these reactions. Flow reactor experiments
are conducted based on these calculations, and small signal gain is measured. When NCl3 is not supplied, absorption of
the I(2P1/2)-I(2P3/2) transition is observed. When NCl3 is supplied, the absorption is decreased and the dip occasionally
turns to the hump, corresponding to a small signal gain of 5×10-3 %/cm. To our knowledge, this is the first observation
of positive small signal gain of the amine-based AGIL system.
Numerical simulation and flow-tube experiments are conducted to understand the chemistry of the amine based all gas-phase
iodine laser (AGIL). The numerical simulation code developed is a one-dimensional, multiple-leaky-stream-tubes kinetics code combined with all the known rate equations to date. The validity of the code is confirmed to compare the calculated results with experimental results reported elsewhere. We find that the key reactions to achieve positive gain are the deactivation reaction of excited iodine atoms by chlorine atoms and the self annihilation reactions of NCl(1Δ). The order of the injection nozzles is crucial to suppress these reactions. It is shown that positive gain is possible with optimized flow rates and nozzle positions. Flow reactor experiments are conducted based on these calculations, and small signal gain is measured. The results are compared with the calculations.
Supersonic chemical oxygen-iodine laser (COIL) with an advanced mixing nozzle is studied. The mixing nozzle consists of a staggered arrangement of thin wedges lying across the flow duct. Its unique shape looks the letter “X” when it is viewed from the side. To use the new arrangement of iodine injector and the X-wing nozzle, 599W of output power with a chemical efficiency of 32.9% was achieved. This is the highest chemical efficiency of any supersonic COIL reported to date.