Thermal tuning of mechanically induced long-period fiber grating

UV Inscription and Pressure Induced Long-Period Gratings through 3D Printed Amplitude Masks

In this work, we demonstrate for the first time the capability to inscribe long-period gratings (LPGs) with UV radiation using simple and low cost amplitude masks fabricated with a consumer grade 3D printer. The spectrum obtained for a grating with 690 µm period and 38 mm length presented good quality, showing sharp resonances (i.e., 3 dB bandwidth < 3 nm), low out-of-band loss (~0.2 dB), and dip losses up to 18 dB. Furthermore, the capability to select the resonance wavelength has been demonstrated using different amplitude mask periods. The customization of the masks makes it possible to fabricate gratings with complex structures. Additionally, the simplicity in 3D printing an amplitude mask solves the problem of the lack of amplitude masks on the market and avoids the use of high resolution motorized stages, as is the case of the point-by-point technique. Finally, the 3D printed masks were also used to induce LPGs using the mechanical pressing method. Due to the better resolution of these masks compared to ones described on the state of the art, we were able to induce gratings with higher quality, such as low out-of-band loss (0.6 dB), reduced spectral ripples, and narrow bandwidths (~3 nm).

Mechanically-Induced Long-Period Fiber Gratings Using Laminated Plates

This work presents a formation method of mechanically-induced long-period fiber gratings using laminated plates. The mechanically-induced long-period fiber grating is temporarily inscribed by compressing the optical fiber between a flat plate and the proposed laminated plate. In turn, the new laminated plate consists of a parallel assembling of single-edged utility blades. We present the experimental characterization of mechanically-induced long-period fiber gratings while employing three laminated plates with a period of 480 ± 20 µm and low duty cycles. These mechanically-induced long-period fiber gratings display a leading rejection band (>15 dB) with a couple of shallow rejection bands (<2 dB) in the range of 1100–1700 nm. This spectral behavior is due to the new mechanical fabrication process that is based on laminated plates that we have proposed, which consists of piling multiple blades with trapezoidal edges that are polished with different levels to obtain different duty-cycles. With the proposed method, we can obtain values of duty-cycles around 10%, much lower than those obtained using traditional methods. Additionally, with this new method, the required mechanical pressure to form the grating is remarkably reduced, which minimizes the probability of the optical fiber failure in the mechanically-induced long-period fiber gratings (MI-LPFGs). Moreover, the proposed mechanically-induced long-period fiber gratings with a single rejection band open the feasibility to implement coarse wavelength division multiplexing systems that are based on long-period fiber gratings.

Demonstration of a microelectromechanical tunable Fabry-Pérot cavity based on graphene-bonded fiber devices

Taking advantage of the high thermal conductivity of graphene, this Letter demonstrates a microelectromechanical (MEM) tunable Fabry-Pérot (F-P) cavity, based on a graphene-bonded fiber device (GFD), which acts as a microheater. By increasing the electric current from 0 to 8 mA in the heater, the temperature of the GFD can rise and approach a value of 760 K theoretically. This high temperature will cause a deformation of the fiber, allowing the graphene-bonded fiber end to form a gap-adjustable F-P cavity with a cleaved single-mode fiber. The gap in the cavity can be reduced by increasing the current applied, leading the transmittance of the cavity to change. In this work, a highly sensitive current sensor (5.9×10⁵  nm/A²) and a tunable mode-locked fiber laser (1.2×10⁴  nm/A²) are created based on the MEM tunable F-P cavity.

Characterization of notched long-period fiber gratings: effects of periods, cladding thicknesses, and etching depths

This study proposes using an inductively coupled plasma etching process to fabricate notched long-period fiber grating (NLPFG) for sensor applications. The effects of the designed parameters (i.e., different fiber cladding thicknesses, grating periods, and etching depths) are studied to explore the characterization of NLPFG. The characterization as indicated by tests of the NLPF showed that the wavelength of NLPFG produced a redshift with decreases in cladding thickness. The drift rate of the wavelength following changes in thickness was -2.801  nm/μm. In addition, a redshift also was exhibited in the increased period, with a wavelength drift rate corresponding to the size of the period of 1.466  nm/μm. Moreover, the results showed that the transmission loss in the spectra increased with etching depth. The variation rate of transmission loss based on etching depth was -0.458  dB/μm.

Tunable Tm-doped fiber ring laser operating at 1.9 μm band using force-induced fiber grating as wavelength tuner

We report wavelength-tunable operation of a Tm-doped silica fiber laser by using a force-induced long-period fiber grating (LPFG) formed in a fiber ring resonator. The laser output wavelength is tuned by moving the transmission passband that is generated between adjacent resonance wavelengths due to the force-induced LPFG. By changing the grating period around 900 μm, we control the laser output wavelength between 1845 and 1930 nm.

Fabrication of a thermally actuated tunable grating and its application as a CO2 laser beam profile analyzer

We propose a thermally actuated tunable grating for measuring the beam profile of a CO(2) laser. The grooves of a transmissive grating are filled with a liquid whose refractive index depends on temperature. A visible laser as a probe and a CO(2) laser as a heat source are illuminated on the grating. The CO(2) laser is absorbed, and depending on its beam profile, a temperature profile is induced on the grating. The refractive index of the heated liquid is changed, resulting in a change of efficiency of the grating for the probe laser. By using the 1st orders of diffraction in a 4f imaging system, the beam profile of the CO(2) laser is imaged onto a CCD camera by the probe laser.

Ultra-widely tunable long-period holey-fiber grating by the use of mechanical pressure

We report an ultra-widely tunable long-period holey-fiber grating, which combines the wide-range single-mode behavior and transverse strain sensitivity of the holey fibers with the advantages of mechanically induced long-period fiber gratings. We obtain a versatile widely tunable long-period holey-fiber grating with attractive transmission spectral characteristics for optical communications, fiber-based amplifiers, and lasers. The mechanically induced long-period holey-fiber grating shows a continuous tuning range over 500 nm, more than 12 dB depth notches with less than 0.75 dB out-of-band losses, and bandwidth control from 10 to 40 nm.