Self-injection linear polarization locking of a fiber laser Christoph Bacher Alexander Heidt Valerio Romano Manuel Ryser

Introduction and motivation Linear polarized sources are essential for a wide range of applications: SHG, SFG, … Not trivial for “non-standard” (1140 – 1160 nm) wavelength Yb-doped fiber lasers Intra-cavity polarization filtering Low efficiency Upcoming parasitic ASE PPLN ω 2ω

Related publications Injection locking is used in a large variety of applications Wavelength stabilization of laser diodes Ventrudo, B. F. et al. “Wavelength and intensity stabilisation of 980 nm diode lasers coupled to fibre bragg gratings” Pliska, T. et al. “Wavelength stabilized 980 nm uncooled pump laser modulesfor erbium-doped fiber amplifiers” Achtenhagen, M. et al. “L-i characteristics of fiber bragg grating stabilized 980-nm pump lasers” Polarization locking of He-Ne laser Cotteverte, J. C. et al. “Polarization dragging in injected lasers” Polarization locking of fiber distributed feedback (DFB) laser Yamashita, S. et al. “Single-polarization operation of fiber distributed feedback (dfb) lasers by injection locking” Hsu, K. et al. “Single-polarization generation in fiber fabry-perot laser by self-injection locking in short feedback cavity”

Setup Bacher, C. et al., “Yellow light generation by frequency doubling of a fiber oscillator” (2016).

Measurement setup

Polarization extinction ratio Signal output power: 2.5 W Error bars ≙ SEM Error bars ≙ 1σ STD

Polarization extinction ratio Error bars ≙ SEM Error bars ≙ 1σ STD

Proof-of-principle Misalignment of HR FBG at port P3

Evolution of optical spectrum @ 1154 nm Bandwidth: 0.04 - 0.06 nm @ -3dB (OSA Resolution: 0.02 nm)

Evolution of optical spectrum Note: Signal @ 1154 nm is attenuated by the HR FBG at port P3 No forward propagating ASE up to 18.8 Watt pump power No Raman scattering

Evolution of backward propagating signal N.B. axis are in linear scale Backward propagating ASE visible at pump power of 18.8 Watt

Conclusion Successfully demonstrated self-injection polarization locking of a fiber laser Polarization extinction ratio of more than 500:1 Output of 2.5 Watt Operation wavelength at edge of gain window @ 1154 nm No forward propagating ASE Negligible backward propagating ASE Outlook Loss of polarization locking above 19 Watt pump power Test of other couplers, e.g. 20/80 Test of other OC FBG

Acknowledgment The fiber group at IAP Thomas Feurer Jonas Scheuner Christoph Lätt as well as Sönke Pilz, Ali El Sayed, Sheida Mahmoodi and Jos Kohn

Thank you for your attention Contact data: christoph.bacher@iap.unibe.ch manuel.ryser@iap.unibe.ch