Thapa, Rajesh2005-11-222005-11-222005-11-22http://hdl.handle.net/2097/133We investigate the nonlinear spectroscopy of acetylene in the near infrared region inside a photonic band gap fiber. The near infrared region of the optical spectrum is an area of intensive research due to its relevance to telecommunication and optical metrology. Acetylene provides a large number of reference transitions coincident with the international telecommunication band. Acetylene contains about 50 strong lines between 1510 nm and 1540 nm in the ν1+ν3 ro-vibrational combination band. We have observed the Doppler-free saturated spectrum of several of these lines. The light from a tunable diode laser at ~1531 nm, resonant with the P(11) transition, is amplified by an erbium doped fiber amplifier and split into a strong pump beam and weak probe beam which counter-propagate inside the gas-filled fiber. The measured Doppler linewidth of the P(11) line at room temperature is about 467 MHz wide. The sub-Doppler profile over a pressure range of 200-1600 mT appears as a narrow absorption feature about 20-40 MHz wide, even at the low pump power of ~10 mW. It is found that for a fiber with an 80 cm length, 20 core size, pumped with 29 mw, the optimum pressure is ~530mT. But the optimum pressure condition will further decrease when the fiber length increases.856559 bytesapplication/pdfen-US© the author. This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s).http://rightsstatements.org/vocab/InC/1.0/Saturation spectroscopy in acetyleneSpectroscopy inside photonic band gap fiberAcetyleneSaturation specroscopySpectroscopy in acetylenePhotonic band gap fiberFiber cellReportPhysics, Optics (0752)