Eloisa Gallegos-Arellano

Analytical Modelling of a Refractive Index Sensor Based on an Intrinsic Micro Fabry-Perot Interferometer

In this work a refractive index sensor based on a combination of the non-dispersive sensing (NDS) and the Tunable Laser Spectroscopy (TLS) principles is presented. Here, in order to have one reference and one measurement channel a single-beam dual-path configuration is used for implementing the NDS principle. These channels are monitored with a couple of identical optical detectors which are correlated to calculate the overall sensor response, called here the depth of modulation. It is shown that this is useful to minimize drifting errors due to source power variations. Furthermore, a comprehensive analysis of a refractive index sensing setup, based on an intrinsic micro Fabry-Perot Interferometer (FPI) is described. Here, the changes over the FPI pattern as the exit refractive index is varied are analytically modelled by using the characteristic matrix method. Additionally, our simulated results are supported by experimental measurements which are also provided. Finally it is shown that by using this principle a simple refractive index sensor with a resolution in the order of 2.15 × 10−4 RIU can be implemented by using a couple of standard and low cost photodetectors.

Finely tunable laser based on a bulk silicon wafer for gas sensing applications

In this work a very simple continuously tunable laser based on an erbium ring cavity and a silicon wafer is presented. This laser can be tuned with very fine steps, which is a compulsory characteristic for gas sensing applications. Moreover the laser is free of mode hopping within a spectral range sufficiently wide to match one of the ro-vibrational lines of a target molecule. Here the proposed laser reached, at ∼1530 nm, a continuous tuning range of around 950 pm (>100 GHz) before mode hopping occurred, when a silicon wafer of 355 μm thickness was used. Additionally, the laser can be finely tuned with small tuning steps of <12 pm, achieving a resolution of 84.6 pm °C-1 and by using a thermo-electric cooler (TEC) the laser showed a high wavelength stability over time. These tuning characteristics are sufficient to detect molecules such as acetylene in which the mean separation between two ro-vibrational lines is around 600 pm. Finally, it is shown that the tuning range can be modified by using wafers with different thickness.

Ytterbium Fiber Laser Based on a Three Beam Optical Path Mach–Zehnder Interferometer

In this letter, a switchable ytterbium doped double cladding photonic crystal fiber (Yb-doped-DCPCF) laser based on a three optical path Mach-Zehnder interferometer (MZI) is presented. Here, the MZI with three-beam path was achieved by fusion splicing a segment of an Yb-doped-DCPCF between two pieces of single mode fibers. Moreover, in the proposed laser arrangement, the Yb-doped-DCPCF segment is acting simultaneously as the MZI and also as the gain medium. This laser can be switched to emit a single or double line by controlling the polarization state and it operates within the range from 1028 to 1033 nm. In addition, the laser emission has a linewidth of 0.07 nm and a single-mode suppression ratio of 40 dB. Finally, it is shown that the fiber laser arrangement is compact and robust and that requires a relativity simple fabrication procedure.

Design of a Fabry-Perot interferometer based on silicon wafer for dielectric gas sensing applications

In this work a design and analysis of a Fabry-Perot interferometer (FPI) based on a silicon wafer for possible application in a SF6 gas sensor used in electric power systems is presented. The sensor design is based on cross correlation spectroscopy principle with an FPI, which acts an optical modulator. Hence, due to characteristics of the FPI transmission spectrum, it can be used detect molecules with very well defined ro-vibrational lines such as those produced by diatomic and linear molecules. The design of the FPI depends mainly of the SF6 absorption wavelength peaks and of the optimum thickness of the silicon wafer. For this reason, in order to measure this absorption peaks a HITRAN database was used. The optimum thickness of the silicon wafer was calculated and simulated transmission spectrum. Finally, we demonstrated by using analytical simulations that a silicon wafer can be implemented as a FPI and used in a SF6 gas sensor.

Temperature sensing setup based on an aluminum coated Mach-Zehnder Interferometer

In this paper a temperature sensing setup based on a Photonic Crystal Fiber (PCF) Mach-Zehnder Interferometer (MZI), coated with aluminum is proposed. Here, this interferometer is fabricated through the concatenation of two sections of Single Mode Fiber (SMF) with a segment of PCF between them. The SMF-PCF joint acts as beam splitter causing the excitement of PCF’s, both cladding and fundamental core modes. In the PCF-SMF union, the cladding modes couple again to the core of the SMF, and interfere with the fundamental core mode, this interaction results in an interference pattern spectrum. Moreover, the MZI was coated with aluminum, using the evaporation technique. By adding a thin metal layer to the PCF section, the general thermal coefficient of the structure changes, enhancing the sensitivity of the device. Experimental results show that a visibility of 13 dBm can be obtained and a sensitivity of 250 pm/°C. Finally, the proposed structure is simple, cost effective and easy to fabricate.

Torsion sensing setup based on a Mach-Zehnder interferometer with photonics crystal fiber

A torsion experimental sensing setup based on a Mach-Zehnder interferometer (MZI) with photonics crystal fiber is presented. The MZI was fabricated by fusion splicing a piece of photonic crystal fiber (PCF) between two segments of a single-mode fiber (SMF). Here, a spectral MZI fringe shifting is induced by applying torsion over the SMF-PCF-SMF. As a result a torsion sensitivity of 35.79 pm/ and a high visibility of 10 dB were achieved. Finally, it is shown that the sensing arrangement is compact and robust.

Torsion sensor with an Yb-doped photonic crystal fiber based on a Mach-Zehnder Interferometer

A Mach-Zehnder Interferometer (MZI) using an ytterbium doped photonic crystal fiber (YbDPCF) is presented as a torsion sensor. The MZI was fabricated by fusion splicing an YbDPCF between two single mode fibers (SMF), which spectral interference pattern is modified by applying torsion over the YbDPCF. For this arrangement the torsion sensitivity achieved was 0.001 nm/°. In addition, experimental results of polarization states and the group birefringence value are provided. This approach is compact, portable and inexpensive and it requires a very simple fabrication procedure.