Femtosecond pulse inscription of a selective mode filter in large mode area fibers

Ria G. Krämer; Christian Voigtländer; Erik Freier; Andreas Liem; Jens U. Thomas; Daniel Richter; Thomas Schreiber; Andreas Tünnermann; Stefan Nolte

doi:10.1117/12.2004349

26 February 2013 Femtosecond pulse inscription of a selective mode filter in large mode area fibers

Ria G. Krämer, Christian Voigtländer, Erik Freier, Andreas Liem, Jens U. Thomas, Daniel Richter, Thomas Schreiber, Andreas Tünnermann, Stefan Nolte

Author Affiliations +

Proceedings Volume 8601, Fiber Lasers X: Technology, Systems, and Applications; 86010S (2013) https://doi.org/10.1117/12.2004349
Event: SPIE LASE, 2013, San Francisco, California, United States

Abstract

We present a selective mode filter inscribed with ultrashort pulses directly into a few mode large mode area (LMA) fiber. The mode filter consists of two refractive index modifications alongside the fiber core in the cladding. The refractive index modifications, which were of approximately the same order of magnitude as the refractive index difference between core and cladding have been inscribed by nonlinear absorption of femtosecond laser pulses (800 nm wavelength, 120 fs pulse duration). If light is guided in the core, it will interact with the inscribed modifications causing modes to be coupled out of the core. In order to characterize the mode filter, we used a femtosecond inscribed fiber Bragg grating (FBG), which acts as a wavelength and therefore mode selective element in the LMA fiber. Since each mode has different Bragg reflection wavelengths, an FBG in a multimode fiber will exhibit multiple Bragg reflection peaks. In our experiments, we first inscribed the FBG using the phase mask scanning technique. Then the mode filter was inscribed. The reflection spectrum of the FBG was measured in situ during the inscription process using a supercontinuum source. The reflectivities of the LP₀₁ and LP₁₁ modes show a dependency on the length of the mode filter. Two stages of the filter were obtained: one, in which the LP₁₁ mode was reduced by 60% and one where the LP₀₁ mode was reduced by 80%. The other mode respectively showed almost no losses. In conclusion, we could selectively filter either the fundamental or higher order modes.

Citation Download Citation

Ria G. Krämer, Christian Voigtländer, Erik Freier, Andreas Liem, Jens U. Thomas, Daniel Richter, Thomas Schreiber, Andreas Tünnermann, and Stefan Nolte "Femtosecond pulse inscription of a selective mode filter in large mode area fibers", Proc. SPIE 8601, Fiber Lasers X: Technology, Systems, and Applications, 86010S (26 February 2013); https://doi.org/10.1117/12.2004349

ACCESS THE FULL ARTICLE

INSTITUTIONAL
Select your institution to access the SPIE Digital Library.

SELECT YOUR INSTITUTION

PERSONAL
Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.

PERSONAL SIGN IN

No SPIE Account? Create one

PURCHASE THIS CONTENT

SUBSCRIBE TO DIGITAL LIBRARY

50 downloads per 1-year subscription

Members: $195

Non-members: $335 ADD TO CART

25 downloads per 1 - year subscription

Members: $145

Non-members: $250 ADD TO CART

PURCHASE SINGLE ARTICLE

Includes PDF, HTML & Video, when available