Line width measurement of semiconductor lasers using quantum interference in electromagnetically induced transparency: a quantum heterodyning method

A technique is described in which electromagnetically induced transparency (EIT) spectra are used to measure laser line width. Two independent sets of EIT measurements are carried out in the presence of $^{85}Rb$ and $^{87}Rb$ atomic isotopes. Conventional self-heterodyning detection is used to obtain standard values of laser line width. A comparison shows that the estimated laser line widths in these measurements are very close to each other

EIT as a tool to observe dual wavelength operation of a semiconductor laser

We propose a simplified technique for dual wavelength operation of an extended cavity semiconductor laser, and its characterization using electromagnetically induced transparency (EIT). In this laser cavity scheme light beam is made converging before it incidences on the cavity grating. The converging angle of the beam creates two longitudinal oscillating modes of resonating cavity. Frequency separation between the longitudinal modes are measured with the help of beat frequency generation in a photodiode and creating pair of EIT spectra in Rb vapor. The pair of EIT dips that are generated due to dual wavelength of this laser (that is used as control laser) can be used to estimate frequency difference between the generated wavelengths. Width of EIT spectra can be used to estimate line width of individual wavelength components

Distribution of polarization vector for evanescent optical near-field

An analysis with the Fresnel formula is presented as possible ways of creating an elliptically polarized evanescent optical field from a linearly polarized laser beam.Under a certain condition a quadrature phase difference is created while light faces total reflection. It has been observed that there is a translational symmetry of the field normal to the plane of incidence (Y-axis); in this direction the field is always linearly polarized. In the other orthogonal directions the field can be elliptically polarized. Looking normal to the plane of the interface (along the Z-axis), one can see an elliptical polarization with varying ellipticity at various z.A circular polarization is also achievable at some particular combination of angle of polarization vector and angle of incidence

Paired electromagnetically induced transparency with dual mode laser: A step towards EIT-Comb

Coupled electromagnetically induced transparency (EIT) has been observed with a dual mode control laser. The technique can be used for generating EIT-comb from optical frequency comb

Line narrowing of electromagnetically induced transparency in Rb with a longitudinal magnetic field

Electromagnetically induced transparency (EIT) experiments in Lambda-type systems benefit from the use of hot vapor where the thermal averaging results in reducing the width of the EIT resonance well below the natural linewidth. Here, we demonstrate a technique for further reducing the EIT width in room-temperature vapor by the application of a small longitudinal magnetic field. The Zeeman shift of the energy levels results in the formation of several shifted subsystems; the net effect is to create multiple EIT dips each of which is significantly narrower than the original resonance. We observe a reduction by a factor of 3 in the D2 line of 87Rb with a field of 3.2 G

Subnatural linewidth for probe absorption in an electromagnetically-induced-transparency medium due to Doppler averaging

We obtain subnatural linewidth (i.e., $<\Gamma$) for probe absorption in room-temperature Rb vapor using electromagnetically induced transparency (EIT) in a \Lambda system. For stationary atoms, the EIT dip for a resonant control laser is roughly one-half as wide as the control Rabi frequency $\Omega_c$. But in thermal vapor, the moving atoms fill the transparency band so that the final EIT dip remains subnatural even when $\Omega _c \gg \Gamma$. We observe a linewidth of $\Gamma /4$ for $\Omega _c = 8\Gamma$ in the $D_2$ line of Rb

Commercial photovoltaic system design for Cardiff City Hall

The rooftops of Cardiff City Hall were surveyed to establish potential areas for commercial-scale photovoltaic (PV) system design. The orientation and tilt angles of suitable unshaded roof areas were measured for accurate PV system simulation. The performance of two PV technologies, polycrystalline silicon (p-Si) and heterojunction with intrinsic thin layers (HIT) was investigated. From the analysis of simulation, experimental, environmental and economic data, HIT was found to be the best-performing PV technology for system installation. Superior performance of HIT under diffuse sunlight conditions, typical of the UK climate, was demonstrated. Additionally, the maximum power temperature coefficient, verified during experimental work, was lower than the p-Si alternative (−0·28 against −0·50%/°C). Electricity demand data for City Hall were analysed and 8·1% of the annual electricity demand (solar fraction) could be supplied by an 88 kWp HIT PV system. The HIT PV system modelled would significantly improve the energy performance of Cardiff City Hall, avoiding >40 000 kg carbon dioxide emissions annually. The levelised cost of energy from one array (B, £0·11/kWh) was less than the current day tariff rate for grid import (£0·1173). The economic and environmental benefits of well-designed high-efficiency PV systems in the UK at commercial scale are also demonstrated