اشترك بالحزمة الذهبية واحصل على وصول غير محدود شمرا أكاديميا
تسجيل مستخدم جديدThreshold of a random laser based on Raman gain in cold atoms
135
0
0.0
(
0
)
تأليف
William Guerin
اسأل ChatGPT حول البحث
ﻻ يوجد ملخص باللغة العربية
We address the problem of achieving a random laser with a cloud of cold atoms, in which gain and scattering are provided by the same atoms. In this system, the elastic scattering cross-section is related to the complex atomic polarizability. As a consequence, the random laser threshold is expressed as a function of this polarizability, which can be fully determined by spectroscopic measurements. We apply this idea to experimentally evaluate the threshold of a random laser based on Raman gain between non-degenerate Zeeman states and find a critical optical thickness on the order of 200, which is within reach of state-of-the-art cold-atom experiments.
قيم البحث
اقرأ أيضاً
Atoms can scatter light and they can also amplify it by stimulated emission. From this simple starting point, we examine the possibility of realizing a random laser in a cloud of laser-cooled atoms. The answer is not obvious as both processes (elas
tic scattering and stimulated emission) seem to exclude one another: pumping atoms to make them behave as amplifier reduces drastically their scattering cross-section. However, we show that even the simplest atom model allows the efficient combination of gain and scattering. Moreover, supplementary degrees of freedom that atoms offer allow the use of several gain mechanisms, depending on the pumping scheme. We thus first study these different gain mechanisms and show experimentally that they can induce (standard) lasing. We then present how the constraint of combining scattering and gain can be quantified, which leads to an evaluation of the random laser threshold. The results are promising and we draw some prospects for a practical realization of a random laser with cold atoms.
Using the transfer matrix method, we numerically compute the precise position of the mobility edge of atoms exposed to a laser speckle potential, and study its dependence vs. the disorder strength and correlation function. Our results deviate signifi
cantly from previous theoretical estimates using an approximate self-consistent approach of localization. In particular we find that the position of the mobility edge in blue-detuned speckles is much lower than in the red-detuned counterpart, pointing out the crucial role played by the asymmetric on-site distribution of speckle patterns.
We study the horizontal expansion of vertically confined ultra-cold atoms in the presence of disorder. Vertical confinement allows us to realize a situation with a few coupled harmonic oscillator quantum states. The disordered potential is created by
an optical speckle at an angle of 30{deg} with respect to the horizontal plane, resulting in an effective anisotropy of the correlation lengths of a factor of 2 in that plane. We observe diffusion leading to non-Gaussian density profiles. Diffusion coefficients, extracted from the experimental results, show anisotropy and strong energy dependence, in agreement with numerical calculations.
Random lasers use radiative gain and multiple scatterers in disordered media to generate light amplification. In this study, we demonstrate a random laser based on diamond nanoneedles that act as scatterers in combination with fluorescent dye molecul
es that serve as a gain medium. Random lasers realized using diamond possess high spectral radiance with angle-free emission and thresholds of 0.16 mJ. The emission dependence on the pillar diameter and density is investigated, and optimum lasing conditions are measured for pillars with spacing and density of 336 nm and ~ 2.9x10^10 cm-2. Our results expand the application space of diamond as a material platform for practical, compact photonic devices and sensing applications.
We experimentally study the coherence time of a below-threshold Raman laser in which the gain medium is a gas of magneto-optically trapped atoms. The second-order optical coherence exhibits photon bunching with a correlation time which is varied by t
wo orders of magnitude by controlling the gain. Results are in good agreement with a simple analytic model which suggests the effect is dominated by gain, rather than dispersion, in this system. Cavity ring-down measurements show the photon lifetime, related to the first-order coherence time, is also increased.
سجل دخول لتتمكن من نشر تعليقات
التعليقات
جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
