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Fiber-feedback optical parametric oscillators

Our frequency converters are based on fiber-feedback technology and combine an intra-cavity passive optical fiber with a bulk nonlinear medium that provides optical gain.

The intra-cavity single-mode fiber does not only result in a compact footprint but provides continuous mode-cleaning for great beam quality, and most importantly stabilizes the temporal dynamics of the oscillator by dispersive feedback. Depending on wavelength this makes our systems 20–100× less sensitive to ambient conditions compared to conventional OPO or OPA systems.

The oscillator runs without active wavelength feedback in normal operation, so piezo tuning loops are not required for day-to-day use. Wavelength settings are highly repeatable. Pump sources include femtosecond and picosecond solid-state and fiber lasers.

Active piezo locking in a conventional OPO versus passive self-synchronization in a Stuttgart Instruments Fiber Feedback OPO
Conventional OPO vs. Stuttgart Instruments FF-OPO: passive self-synchronization keeps the system locked as the cavity drifts – no active electronics required.
Block schematic of the Fiber Feedback OPO: pump, nonlinear crystal, output coupler, single-mode fibre that stretches the pulse in time, diffraction grating and delay line that selects the amplified wavelength by timing
Signal path through the cavity: the fibre stretches the pulse in time (chirp), the grating sets the colour dispersion, and the delay line shifts the pump in time to amplify the chosen wavelength.

FAQ

Frequently asked questions

We use a hybrid concept of fiber-feedback and parametric gain in a bulk nonlinear crystal. The intra-cavity fiber acts as a mode-cleaner and pins the pointing.
The intra-cavity fiber is single-mode, so it guides only the fundamental transverse mode. Higher-order spatial modes couple poorly into the fiber and stay below threshold, so the oscillator runs in a clean, near-diffraction-limited TEM00 beam. Because the output beam is defined by the fiber, its pointing is fixed and repeatable – independent of free-space alignment drift. The same fiber also provides the dispersive feedback used for tuning, so beam-cleaning and tuning share one passive element.
We use dispersive stretching of our feedback pulse. By adjusting the timing between pump and feedback pulse we can tune continuously and gap-free with < 0.05 nm accuracy.
The fiber is passive and does not add ASE. The Alpha tracks the pump laser’s relative intensity noise; specified RIN is typically < −160 dBc/Hz. Temporal pulse contrast below 130 dB has been measured (M. Floess et al., Opt. Express 30(1), 1 (2022)).
The system is fully automated and provides a websocket interface (ethernet or WiFi connection) that can be accessed with any common programming language. The included GUI is written in C++, but comes with templates in Python and LabVIEW. Simultaneous access from multiple clients is possible (e.g. watching the laser with the Stuttgart Instruments GUI and triggering wavelength steps by a Python routine).
They are fiber-feedback OPOs (FF-OPO): a compact OPO cavity with passive fiber feedback. The design is passively stable over long periods and preserves the low RIN of the pump in typical configurations.

Still have questions? Contact us.