Bandwidth of laser improve in fiber communication

Bandwidth of laser improve in fiber communication

  • 2021-11-19

When manufacturing high-speed lasers, the following measures can be taken to improve the 3dB bandwidth of the device: 

1.In the active region, strain (compensated) multi-quantum well structure is adopted

The quantum well laser trap material is at the top of the heavy hole level of the valence band due to the biaxial compressive strain parallel to the well plane and the tensile strain perpendicular to the well plane Rises, and the valence band back degenerate, split the electrons from the spin orbit to heavy cavity with the transition probability of approximately equal zero, reduce the auger recombination probability at room temperature, thus resulting in a decline in the quantum well laser threshold current and linewidth enhancement factor decreases and the relaxation oscillation frequency, modulation bandwidth and the differential gain coefficient significantly improved.

2.P-type doping in the active region

p-type doping can reduce the hole transport through the SCH region, which is the main limitation for high-speed quantum well devices. P-type doping can obtain very high differential gain, and make the distribution of carriers in the quantum well more uniform.

If the Zn doping concentration in the active region is close to 1018 cm-3, its 3dB bandwidth can reach 25GHz, and the oscillation frequency of the device can be increased to 30GHz(cavity length is 300μm). In addition, there are conducive to reduce heavily doped linewidth enhancement factor and further improve the differential gain, these are beneficial to improve the modulation characteristics of the device.

3.Reduce the parasitic parameters of electricity

In order to reduce the high speed laser electrical parasitic parameters, especially the parasitic capacitance, can use half insulation Fe - InP regrowth landfill technology, at the same time also need to reduce the electrode area; Using self-aligned narrow mesa structure (SA-CM) to reduce parasitic capacitance Polyimide filling method is often used to reduce parasitic capacitance.

4.Improve the photon concentration and differential gain inside the laser

The intrinsic resonant frequency can be increased by increasing the photon concentration in the laser cavity. The differential gain can be improved by using DFB structure to make the lasing wavelength and the gain peak wavelength negative detuning (-10nm), which can increase the -3dB modulation bandwidth.

© hak cipta: Shanghai Shinho Fiber Communication Co., Ltd. Seluruh hak cipta.


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