Fiber-Enhanced Raman Multigas Spectroscopy: A Versatile Tool for Environmental Gas Sensing and Breath Analysis

Abstract

Versatile multigas analysis bears high potential for environmental sensing of climate relevant gases and noninvasive early stage diagnosis of disease states in human breath. In this contribution, a fiber-enhanced Raman spectroscopic (FERS) analysis of a suite of climate relevant atmospheric gases is presented, which allowed for reliable quantification of CH4, CO2, and N2O alongside N2 and O2 with just one single measurement. A highly improved analytical sensitivity was achieved, down to a sub-parts per million limit of detection with a high dynamic range of 6 orders of magnitude and within a second measurement time. The high potential of FERS for the detection of disease markers was demonstrated with the analysis of 27 nL of exhaled human breath. The natural isotopes (13)CO2 and (14)N(15)N were quantified at low levels, simultaneously with the major breath components N2, O2, and (12)CO2. The natural abundances of (13)CO2 and (14)N(15)N were experimentally quantified in very good agreement to theoretical values. A fiber adapter assembly and gas filling setup was designed for rapid and automated analysis of multigas compositions and their fluctuations within seconds and without the need for optical readjustment of the sensor arrangement. On the basis of the abilities of such miniaturized FERS system, we expect high potential for the diagnosis of clinically administered (13)C-labeled CO2 in human breath and also foresee high impact for disease detection via biologically vital nitrogen compounds.

[INVITED] New perspectives in photonic crystal fibre sensors

“…The possibility of sensing multiple parameters with multi-core or photonic band gap (PBG) PCFs was demonstrated in recent years [81][82][83]. PBG fibres have a hollow core and guide light with low attenuation within a narrow spectral range which is sufficient to guide the pump laser light and the Raman-scattered photons [82,83].…”

“…The holey structure of PCFs offers an additional degree of freedom in the design of optical sensors as they can be infiltrated with liquids, gases or nanomaterials [16][17][18][19][20][21][22][23]. In most cases the PCF plays also the role of gas or liquid chamber.…”

“…This gives rise to a strong light-matter interaction, hence to high sensitivity. The complexity of the setups to infiltrate gases, liquids or nanoscale materials in the PCFs [16][17][18][19][20][21][22][23] is an issue that must be minimised otherwise it will be difficult to find practical applications of PCFs for gas or liquid sensing. On this regard, PCF sensors can benefit from the advances in micro-and opto-fluidics and nanotechnology.…”

Spontaneous Raman scattering in hollow core photonic crystal fibres

“…Hollow core photonic crystal fibres (HC-PCFs) [1] have recently been used to overcome this challenge [2][3][4][5][6]. In a HC-PCF, light is guided with low attenuation in an air core.…”

“…Using this format, detection of both forward and backward Stokes signals has been demonstrated. Additionally, sensitivities as low as 0.2 ppm of methane have been achieved [6].…”