Π‐Electron‐Extended Porphyrin‐Linked Covalent Organic Framework for a Q‐Switched All‐Solid‐State Laser

Herein, a new π‐electron‐delocalized building block (ProPh‐4CHO) is reported for the construction of a π‐electron‐extended porphyrin/pyrene‐linked covalent organic framework (ProPh‐PyTA‐COF) for use as a saturable absorber (SA) in a Q‐switched all‐solid‐state laser. Employing a mode‐locked fiber laser operated with 130‐fs pulses at 1030 nm and a repetition rate of 28 MHz, ProPh‐PyTA‐COF exhibits remarkable optical nonlinear absorptions: two saturable absorptions with saturation intensities of 92 MW cm−2 and 1 kW cm−2. This material is used to fabricate the first pulsed Q‐switched all‐solid‐state laser incorporating a COF as an absorber. The laser incorporating this COF‐SA exhibited a pump power of 6.5 W with a pulse duration of 1.2 μs, corresponding to a pulse repetition rate of 94.4 kHz. This study not only reveals the possibility of using saturation absorption to pulse a solid‐state laser but also opens up a new path toward optical nonlinearity through the engineering of π‐bond delocalization.