Contents I. Introduction
High-power single-mode semiconductor lasers operating at wavelengths near with the characteristics of low transmission loss, eye-safety, and high anti-interference ability are widely used in applications such as optical communication, light detection, laser guidance, medical treatment and photon integration [1], [2], [3], [4], [5]. Different structures have been reported and achieved good performances, such as integrated moiré grating [3], three-section MOPA [4] and sidewall Bragg grating monolithically integrated with a curved tapered semiconductor optical amplifier [5]. However, these devices are mainly based on the mode selection of the distributed feedback (DFB) fabrication technology, which utilizes the electron beam exposure or the combination of holographic exposure and photolithography to pattern gratings, requiring complex process steps. Surface gratings can simplify the process of fabrication to a certain extent, but is still difficult to be fabricated, especially for low-order surface gratings, just like first-order gratings or second-order gratings. The nano-level pattern of low-order gratings requires the application of high-resolution photolithography technology, resulting in high manufacturing costs. Introducing micron-level slots on the surface of the ridge for wavelength selection can avoid the complex regrowth process and the high-precision photolithography. But so far, all the reported slotted lasers [6], [7], [8], [9] we know operate at relatively low output power (< 50mW). For high power semiconductor lasers, affected by the contradiction between the size of the devices and the parasitic parameters, the larger the active area size is, the higher the light power is. At the same time, the parasitic capacitance is also large, resulting in the poor modulation characteristics of the devices. Therefore, the modulation bandwidth of high-power semiconductor lasers is generally low, which is not conducive to the actual application of the devices.
