Intra-cavity amplification Fourier domain mode locked laser

•A new class of structure for amplifying output power without any optical device outside the cavity is presented.•The output power of the new structure is several or even multiple times of the traditional structure.•The performance of the new structure is suitable for different length delay lines. Fourier domain mode locked (FDML) lasers are excellent tunable laser sources for swept source optical coherence tomography (SS-OCT) systems because of their aggregate of high sweep rates, large tuning ranges, and excessive output powers. However, conventional FDML lasers provide high output powers of only use the out of cavity amplification technology, resulting in complex structure and high cost. Here, we describe intra-cavity amplification Fourier domain mode locking (IA-FDML), a new class of design for amplifying output power without any optical device outside the cavity. A detailed structure framework is provided and the comparison of the output waveforms of traditional FDML and IA-FDML laser with different length delay lines are discussed. The wavelength-swept laser is capable of FWHM scanning range of more than 103 nm at 65.76 kHz sweeping rate. The measured axial resolution of the forward scan is 5.8 μm in air and 4.14 μm in tissue. This advance enables high-speed, high-power SS-OCT imaging without the need for extra-cavity amplification, significantly reducing laser cost and complexity.