Diode-pumped Tm:KY(WO₄)₂ laser passively modelocked with a GaSb-SESAM

We present the first diode-pumped modelocked thulium (Tm³⁺) laser based on a double-tungstate crystalline gain material. The solid-state laser consists of a Tm:KY(WO₄)₂ crystal as gain medium and a GaInSb/GaSb quantum well saturable absorber for self-starting passive mode locking. The laser is pumped by a multi-mode fiber-coupled laser diode at a wavelength of 793 nm. An average output power of 202 mW is achieved at a center wavelength of 2032 nm. Pulses with duration of 3 ps are generated at a repetition rate of 139.6 MHz. We also report on the first noise evaluation of a modelocked solid-state laser operating in the 2-µm wavelength range. We measured a timing jitter of sub-100 fs and a relative intensity noise of only 0.04% (frequency range from 500 Hz to 1 MHz).