外部凹面鏡を用いた能動モード同期VCSELの高繰り返し周波数・低閾値電流動作(超高速伝送・変復調・分散補償技術,超高速光信号処理技術,広帯域光増幅・WDM技術、受光デバイス,高光出力伝送技術,一般,(ECOC報告)) Active mode-locked VCSEL using external concave mirror with high repetition rate and low threshold current

面発光レーザ(Vertical cavity surface emitting laser; VCSEL)を用いた能動モード同期レーザによる31GHzの高い繰り返し周波数と1mA程度の低い閾値電流動作を同時に実現した.光インターコネクション用の光源として期待されているVCSELを用いた光クロック光源の実現を目指し,凹面鏡を用いた複合共振器構造を導入したVCSELを設計した.VCSELの上部DBRと外部凹面鏡の反射率を,高い繰り返し周波数と低い閾値電流を両立するように最適化した.VCSELと凹面鏡の位置を調整し,単一横モード,多縦モード発振を実現した.サブハーモニック能動同期によって,VCSELの直接変調帯域を大きく超えた高速モード同期を実現した.

We demonstrated the active mode-locking using a VCSEL with a high repetition rate of 31GHz and a low threshold current of about 1mA. VCSEL is a candidate for the light sources of the optical interconnection. We designed a composite resonator VCSEL, which consists of a VCSEL and an external cavity formed by a concave mirror. The reflectivity of the top-DBR of the VCSEL and the external concave minor was optimized to realize low threshold current and high repetition rate simultaneously. The mutual position between the VCSEL and the external concave minor was optimized to realize the single-transverse and multi-axial mode oscillation. By applying sub-harmonic frequency modulation to the VCSEL, optical signal of as high as 31GHz was obtained. The repetition frequency is much higher than that of the direct modulation bandwidth of the VCSEL used.