Abstract
Semiconductor optical amplifiers (SOAs) offer direct electrical injection, power consumption, integration, and anti-radiation advantages over optical fiber amplifiers. However, saturation output power and gain bandwidth have been limited in traditional structure SOAs. We demonstrate a monolithic integrated SOA with broad spectrum, high power, high gain, and small spectral linewidth expansion. The device adopts a two-stage amplified large optical cavity structure, and a lower optical field confinement factor is obtained by adjusting the thickness of the waveguide layer. The lower optical field confinement factor is conducive to improving the coupling efficiency and the maximum output power. Our device, fabricated only by standard i-line lithography with micron-scale precision, obtains excellent and stable performance. When the input power is set to 1 mW, the output power is 419 mW with a gain of 26.23 dB. When the input power is set to 25 mW at 25 °C, the output power increases to 600 mW with a gain of 13.8 dB. The corresponding gain bandwidth of 3 dB measures at least 70 nm. The spectral linewidth after the SOA is 1.15 times wider than that of the seed laser.
Highlights
High-power optical amplifiers are required for an increasing number of applications, including free space optical communication, light laser detection and ranging, absorption spectroscopy, biomedical imaging, microwave photonic (MWP) analog signal processing, and low-noise mode-locked lasers for photonic analog-to-digital converters [1]–[8]
As the light propagates from the input end of the amplifier to the output end, the width of the waveguide gradually increases; this structure ensures that most of the light remains in the default mode and provides gain with a high saturation output power while reducing heat generation and catastrophic optical damage (COD)
The previous analysis shows that ideally the effective facet reflectivity of the SOA should be zero, so that the photons will not generate resonance amplification in the gain medium. This is impossible to achieve in practice, and even a small reflection will cause some disturbance in the amplified spontaneous emission (ASE) spectrum
Summary
High-power optical amplifiers are required for an increasing number of applications, including free space optical communication, light laser detection and ranging (lidar), absorption spectroscopy, biomedical imaging, microwave photonic (MWP) analog signal processing, and low-noise mode-locked lasers for photonic analog-to-digital converters [1]–[8]. As the light propagates from the input end of the amplifier to the output end, the width of the waveguide gradually increases; this structure ensures that most of the light remains in the default mode and provides gain with a high saturation output power while reducing heat generation and catastrophic optical damage (COD). The previous analysis shows that ideally the effective facet reflectivity of the SOA should be zero, so that the photons will not generate resonance amplification in the gain medium This is impossible to achieve in practice, and even a small reflection will cause some disturbance in the amplified spontaneous emission (ASE) spectrum. The spectrum shows a background signal due to ASE, and while the ASE signal is reduced once the amplifier is pumped with seed laser, no further reduction is seen for greater input powers This is attributed to the saturation of the SOA. The SOA output light was attenuated to a safe power level by another optical isolator and a variable
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