저전류 동작을 위한 Ridge Waveguide MQW Laser Diode의 최적 설계 및 제작에 관한 연구

Abstract

Ridge waveguide MQW LD is widely used 10, 100, 150Mbps light source of optical communication systems. But the accurate theoretical analysis is insufficient due to having an intermediate characteristics between gain-guide and index-guide in the structure.

Therefore, in this thesis, the optimal waveguide structure of ridge waveguide LD was modeled and calculated by the theoretical analysis to operate index-guide, low current and single mode. Ridge waveguide MQW LD was fabricated by vertical LPE equipment based on the calculated data, and the fabricated LD was measured.

The lateral index step of ridge waveguide MQW LD was calculated to operate index-guided LD according to thicknesses of upper cladding and buffer layers. As a result, critical index step is about 14×10-3.

In order to operate single mode, index-guide and low threshold current, the maximum width of ridge was calculated according to the index steps. The results show that the width of ridge must be less than 3㎛.

On the basis of designed values, MQW DH wafer was grown to fabricate ridge waveguide MQW LD by vertical LPE apparatus and the ridge shape was formed by photolithography and wet etching processes to 3㎛ ridge width and the electrode was deposited.

When the cavity length was 300㎛, the measured results of the electrical and optical characteristics were as follows : the threshold current was 17㎃, the differential efficiency was about 23%, the characteristic temperature was 42K, the temperature dependence of the lasing wavelength was 5.84Å/℃, far-field-pattern is 17°× 36.5°

When it was compared measurement with numerical analysis, we obtained similar results, compared with the commercial RWG MQW LD confirmed to operate index guide, low threshold current, single mode.