Electromagnetically Induced Transparency in Sodium Dimer

Abstract

We have investigated the electromagnetically induced transparency (EIT) in the diatomic sodium system with three different detection methods Using the optical-optical double resonance (OODR) spectroscopy two different combination of ladder-type three-level system in the sodium dimer (X^1 Σ_g^+ (15 73) →B^1 Π_u (13 74)→3^1 Π_g (8 75) and X^1 Σ_g^+ (5 55)→B^1 Π_u (9 56)→3^1 Π_g (4 55)) have been constructed and confirmed by detecting the total fluorescence from the triplet upper state First the total fluorescence signal was detected by a filtered photomultiplier (PMT) Once the EIT occurs a sharp dip will appear in the middle of the total fluorescence signal because of the sharply decreased population of the upper state However the EIT was not observed since the total fluorescence of the triplet upper state is from the population which went through the “decoherent process”; the coherence phenomena such as EIT is difficult to be observed with this detection method Second either the population of the intermediate state and the upper state was monitored by directly recording the fluorescence back to the intermediate state and ground state respectively through a monochromator The state-selected fluorescence signals from the intermediate states of two selected three-level system were detected and could be labeled However the signal did not be affected by the coupling laser (Toptica laser) Moreover for the fluorescence signals from the upper state there was no expected signal appearing in the estimated wavelength Since the pump laser (should be probe laser in the ordinary ladder-type EIT) in our system was provided by the Ar^+ laser with 10GHz laser linewidth the molecules can only absorb certain part of the laser field Therefore the transmitted signal of the Ar^+ laser must be accompanied with a large DC background noise To overcome this problem we tried to detect the transmitted signal of the Toptica diode laser (coupling laser) which is a narrow band laser (linewidth: 0 5 MHz) However the EIT phenomena still not be observed in this method Although the EIT phenomena was not observed in this study we have proposed a new system (still diatomic sodium system but different selected states) which consists of two narrow linewidth tunable ring laser We believe the EIT phenomena must be observed in such system

Date of Award	2016 Nov 2
Original language	English
Supervisor	Chin-Chun Tsai (Supervisor)