Intra-cavity spectroscopy using amplified spontaneous emission in fiber lasers

Norhana Arsad, Min Li, George Stewart, Walter Johnstone

Research output: Contribution to journalArticle

9 Citations (Scopus)

Abstract

Fiber laser sources offer interesting possibilities for gas sensors since they can operate over an extended wavelength range, encompassing the near-IR absorption lines of a number of important gases but a major problem is that overtone absorption lines of gases in the near-IR are relatively weak. In order to enhance sensitivity, we present here a simple method of intra-cavity absorption spectroscopy (ICAS) which makes use of the amplified spontaneous emission (ASE) already present within a fiber laser cavity. The ASE also provides a convenient broadband source for the simultaneous interrogation of several gases within the gain-bandwidth of the fiber laser. The key principle is based on adjusting the cavity attenuation to select an appropriate inversion level where the fiber gain curve is flat. Under this condition, the ASE undergoes multiple circulations within the fiber laser cavity, enhancing the effective path-length of a gas cell placed within the laser cavity. A theoretical model of system operation is given and we have experimentally demonstrated the principle of operation with acetylene and carbon dioxide using a simple erbium fiber laser system containing a 6 cm path-length, fiber coupled, intra-cavity, micro-optic gas cell. We have experimentally simultaneously observed 16 absorption lines for 1% acetylene gas in the 1530 nm region and detected the very weak carbon dioxide lines in this same wavelength region. A path length enhancement of ∼500 in the linear regime has been demonstrated transforming the 6 cm micro-optic cell into an effective path length of ∼30 m. We also demonstrate how the enhancement factor may be calibrated by use of a simple fiber-optic interferometer. Apart from the OSA, all components are inexpensive and the system is very simple to construct and operate.

Original languageEnglish
Article number5677567
Pages (from-to)782-788
Number of pages7
JournalJournal of Lightwave Technology
Volume29
Issue number5
DOIs
Publication statusPublished - 2011

Fingerprint

spontaneous emission
fiber lasers
cavities
gases
spectroscopy
laser cavities
acetylene
carbon dioxide
cells
optics
fibers
augmentation
interrogation
dioxides
wavelengths
erbium
fiber optics
absorption spectroscopy
interferometers
attenuation

Keywords

  • erbium-doped fiber lasers
  • fiber sensors
  • gas sensors
  • Intra-cavity spectroscopy
  • laser spectroscopy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Intra-cavity spectroscopy using amplified spontaneous emission in fiber lasers. / Arsad, Norhana; Li, Min; Stewart, George; Johnstone, Walter.

In: Journal of Lightwave Technology, Vol. 29, No. 5, 5677567, 2011, p. 782-788.

Research output: Contribution to journalArticle

Arsad, Norhana ; Li, Min ; Stewart, George ; Johnstone, Walter. / Intra-cavity spectroscopy using amplified spontaneous emission in fiber lasers. In: Journal of Lightwave Technology. 2011 ; Vol. 29, No. 5. pp. 782-788.
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