Long period fibre gratings inscribed by sinusoidal intensity modulated femtosecond laser

2021 ◽  
Author(s):  
Xiaofan Zhao ◽  
Hongye Li ◽  
Binyu Rao ◽  
Meng Wang ◽  
Baiyi Wu ◽  
...  
Keyword(s):  
Refractive Index ◽  
Femtosecond Laser ◽  
Insertion Loss ◽  
Transmission Spectrum ◽  
Grating Period ◽  
Higher Order ◽  
Modulation Method ◽  
Long Period ◽  
Intensity Modulated ◽  
Harmonic Resonance

Abstract To the best of our knowledge, this is the first study to propose and verify a novel and simple direct inscription method for long-period fibre gratings (LPFGs) with an arbitrary grating period using a sinusoidal intensity modulated femtosecond laser. This method induces a sine refractive index (RI) modulation, which makes the LPFGs have no higher-order harmonic resonance that exists in the normal square-wave modulation method. This is beneficial for reducing the insertion loss of the LPFGs and optimising the transmission spectrum. Using this method, we also conveniently realise the inscription of superimposed, apodised, and chirped LPFGs. This work presents a simple but effective inscription scheme for various types of LPFGs using a femtosecond laser.

scholarly journals Highly refractive index sensitive femtosecond laser inscribed long period gratings

2011 ◽  
Author(s):  
Edward Davies ◽  
Kyriacos Kalli ◽  
Charalambos Koutsides ◽  
Lin Zhang
Keyword(s):  
Refractive Index ◽  
Femtosecond Laser ◽  
Long Period ◽  
Long Period Gratings

Sensing Characteristics of Long-Period Grating Inscribed in Grapefruit Photonic Crystal Fiber by Femtosecond Laser

2014 ◽  
Vol 513-517 ◽  
pp. 4231-4234
Author(s):  
Yuan Wei ◽  
Yu Jie Du
Keyword(s):  
Refractive Index ◽  
Photonic Crystal ◽  
Femtosecond Laser ◽  
Photonic Crystal Fiber ◽  
Resonant Wavelength ◽  
Long Period Grating ◽  
Crystal Fiber ◽  
Long Period ◽  
Surrounding Refractive Index ◽  
Novel Method

A novel method for fabricating long period grating in grapefruit photonic crystal fiber (GPCF) is proposed and demonstrated. An 800nm femtosecond laser is adopted to scan a section of GPCF periodically point-by-point, resulting in effective refractive index periodic demodulation. High resonance of ~17dB is obtained with a grating length of 30 mm. The temperature sensitivity of resonant wavelength 0.03 nm/°C is obtained from 20°C to 120 °C. In addition, the relationship between resonant wavelength and surrounding refractive index (SRI), when LPFG immersed in refractive index of solution of different index, is also researched.

Modelling and analysis of chirped long-period grating inscribed in a planer optical waveguide structure for sensing applications

2020 ◽  
Vol 0 (0) ◽  
Author(s):  
Adarsh Chandra Mishra ◽  
Krishnendu Dandapat ◽  
Saurabh Mani Tripathi ◽  
Pooja Lohia ◽  
Dilip Kumar Dwivedi
Keyword(s):  
Refractive Index ◽  
Electric Field ◽  
Optical Waveguide ◽  
Transmission Spectrum ◽  
Resonance Structure ◽  
Field Equations ◽  
Long Period Grating ◽  
Refractive Index Sensitivity ◽  
Long Period ◽  
Sensing Applications

AbstractA chirped long-period grating inscribed in a planer optical waveguide sensor is demonstrated. The distribution of electric field within the structure has been obtained using boundary condition for the electric field equations at different dielectric boundaries. The transmission spectrum of the proposed sensor is obtained by transfer-matrix method. Further, the sensitivity for ambient refractive index and temperature has been analysed by observing the shift in resonance wavelengths. The presence of two dips in the transmission spectrum effectively doubles the sensitivity in comparison to the single resonance structure. We have achieved refractive index sensitivity of 5600 nm/RIU and temperature sensitivity of 0.8 nm/ °C, respectively.

LASER DIRECT WRITING OF LONG PERIOD FIBER GRATING BY 800 NM FEMTOSECOND LASER PULSES

2008 ◽  
Vol 17 (04) ◽  
pp. 425-433 ◽  
Author(s):  
SHUANGCHEN RUAN ◽  
YI HUANG ◽  
CHENLIN DU ◽  
YONGQIN YU
Keyword(s):  
Refractive Index ◽  
Femtosecond Laser ◽  
Transmission Loss ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Direct Writing ◽  
Loss Peak ◽  
Laser Direct Writing ◽  
Time Duration ◽  
Long Period

Femtosecond laser pulses with ultrashort time duration and ultrahigh peak power can cause the refractive index change in transparent materials and micron scale machining precision. Long period fiber gratings (LPFGs) with different periods and different grating lengths in the standard single mode fiber were fabricated, using laser direct writing method, by femtosecond laser pulses with pulse width of 200 fs at a center wavelength of 800 nm in air. The transmission spectra were studied in the range of 1510 nm to 1610 nm. Two LPFGs with period of 400 μm, and 550 μm, respectively fabricated with same irradiation power of 275 mW, were shown. The loss peak of 1552 nm, the transmission loss of 16 dB and the FWHM of 20 nm were obtained when the period of LPFG was 400 μm, while the loss peak of 1588 nm, the transmission loss of 20 dB and the FWHM of 25 nm were achieved when the period of LPFG was 550 μm. According to the theory of mode field coupling for long period grating, it was indicated that the modulation of refractive index Δn was in the level of 10-2.

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