Background Combined irradiation of continuous-wave (CW) and pulsed lasers can markedly modify macroscopic effect thresholds in laser processing, driving strong demand for CW-pulse integrated fiber laser (CPIFL) sources toward intelligent high-efficiency processing. However, existing CPIFL schemes combine multiple beams of different temporal formats through port switching or spatial beam combining, suffering from complex architectures, non-coaxial optical paths, inconsistent spot sizes, and degraded robustness. Directly generating multiple temporal formats within a single fiber laser would eliminate these limitations, but remains challenging: CW output is mainly limited by transverse mode instability (TMI), pulsed output by stimulated Raman scattering (SRS) and amplified spontaneous emission (ASE), and their coupling severely restricts power scaling and stability.

Purpose This work aims to realize stable monolithic output of single-wavelength CPIFL from a monolithic fiber laser through temporal gain modulation, thereby achieving selective and stable amplification of temporal-domain power.

Methods A temporal gain modulation method combining a CW seed with CW-pulse integrated pumping was implemented in a master oscillator power amplifier configuration. A 22.1 W CW seed at 1080 nm was injected into the amplifier stage based on a 30 m Yb-doped fiber (core/cladding diameters of 30/600 μm, effective mode-field area of about 487.6 μm², absorption coefficient of about 1.41 dB/m at 976 nm). The 976 nm laser-diode pump, launched through an (18+1)×1 pump-signal combiner, was divided into CW and pulse-modulated parts (repetition frequency of 1 kHz, duty cycle of 10%) via a self-developed integrated CW-pulse drive and control system, and the laser was delivered through a cladding power stripper and an output end cap.

Results The average output power increased linearly with pump power, reaching 1542.0 W at the maximum average pump power of 1977.1 W (CW pump component of 1075.2 W), corresponding to an optical-to-optical conversion efficiency of 76.9%. At the maximum power, the peak power was 6479.3 W, the CW component power was 1005.7 W, the modulation depth was 73.1%, and the pulse width was 95.7 μs, with pulse waveforms free of relaxation-oscillation spikes. The frequency domain characteristics exhibited a dominant peak at 1 kHz with a signal-to-noise ratio of 60.8 dB, and the Raman suppression ratio reached 40.8 dB. Beam quality factors of M_x^2=1.50 and M_y^2=1.46 were measured at an average output power of 740.0 W. The laser operated stably for about 3 min at the maximum power, with no evident changes in output power, spectrum, or temporal waveform.

Conclusions Pump temporal modulation alone enables selective and stable amplification of temporal-domain power in a monolithic fiber, offering good structural adaptability and versatility. Combined with our previous oscillator-based work, a complete CPIFL technology chain from oscillator to amplifier is preliminarily established. Optimizing fiber devices and pump temporal parameters to jointly suppress SRS, TMI, and ASE, together with developing adaptive temporal control strategies, is expected to further extend the output power and intelligent control capability of monolithic CPIFLs.