Fig. 2: Schematic and characteristics of edge-emitting, actively Q-switched semiconductor laser.

a The alternatively placed gain and Q-switch regions (52 pairs) in the cavity of 4 mm are electrically separated in the lateral direction. b A voltage (VLD) ranging from 4.45 to 5.04 V was applied to the gain region. Then, a pulsed current is input through a low-side n-type metal–oxide–semiconductor (NMOS) driver. Three states exist for the Q-switch anode: high impedance with parasitic capacitance, VDD (5 V) via a p-type metal–oxide–semiconductor (PMOS), or ground via an NMOS. Each timing is precisely controlled by a pulse signal generator embedded in the complementary metal-oxide-semiconductor (CMOS) driver with a least significant bit (LSB) equivalent to ~100 ps. c Streak camera (Hamamatsu Photonics C5680) images of the laser pulses at \(\Delta {t}_{{{\mathrm{lsd}}}}=3.17\) ns and\(\Delta {t}_{{{\mathrm{lsd}}}}=5.22\) ns. The rainbow scale represents the linear intensity. Notably, the time offsets observed in the images are induced by a jitter of the streak camera and do not reflect the actual timing of the pulsed laser oscillation. d Temporal waveform of the laser pulse at \(\Delta {t}_{{{\mathrm{lsd}}}}=5.22\) ns. e, f Peak power, average power, pulse width, wavelengths of pulse and tail, and ratio of tail depending on \(\Delta {t}_{{{\mathrm{lsd}}}}\). Pulse energy is calculated by dividing the average power by the repetition rate of 3.16 MHz. The peak power is determined from the laser pulse waveform. g Temporal waveform of seven laser pulses, demonstrating stable pulse generation. h Beam quality factor (M²) of a similar semiconductor laser not integrated into the module. Focal position shift is attributed to the large aspect ratio of the beam divergence angles. The distance from the collimator lens to an f = 40 mm lens for the M² measurement is ~250 mm. Therefore, the lens is positioned within the Rayleigh length for the vertical component and beyond the Rayleigh length for the horizontal component. The focal point along the horizontal axis is theoretically determined to be 47.6 mm, in agreement with the experimental results. For the module, the aspect ratio is adjusted using anamorphic optics.