Highly efficient operation and uniform characteristics of curved mirror vertical-cavity surface-emitting lasers

Abstract

This study obtained highly uniform and efficient GaN-based vertical-cavity surface-emitting lasers (VCSELs) with curved mirror from a single wafer. The average threshold current (Ith) and the optical output power (Pmax) of 14 nominally identical chips measured up to 7 mA were 0.64 mA and 4.5 mW, respectively. The standard deviations of Ith and Pmax were 0.043 mA and 0.23 mW, respectively. Additionally, the best chip shows maximum values of wall plug efficiency and output power of 13.4% and 7.6 mW, respectively, at 5.2 mA and 12.8 mA operating currents.

Highly-efficient operation and mode control in GaN-based VCSELs with a curved mirror

“…This frequently results in a fabrication error, which can deteriorate the lasing yield. Using a long-cavity structure, lasing with 100% yield and good uniformity of I-V/L have been reported, which support that this structure is stable against fabrication disturbances [13].…”

“…The impact of any loss due to the addition of the filtering mirror was approximately evaluated considering the SE relative to that of the reference DBR structure. It has previously been reported that a device with a 7.5-pair DBR (99.3% reflectivity) showed an SE of 0.83 W A −1 with an internal loss on the order of 1% [19]. Assuming a constant injection efficiency and wavelength, SE comparison provides the internal loss, αi, in an FM sample as follows:…”

“…Curved-mirror VCSEL devices were fabricated similarly to the method in Ref. [12][13]; their structures are shown in Fig. 2(c) and are briefly described below.…”

“…After the report of operation under pulsed current injection in 2018 [9], blue VCSELs with similar structures, efficient current confinement by ion implantation [10], sub-milliampere operation [11], stabilized lateral modes [12], high efficiency operation up to 13.5% [13] (see Figure 1a), long life reaching 2000 h [14], generation of spatially coherent dot array of VCSEL modes [15], and narrow emission angle of 3.9° for circular aperture [16] and 0.5 degree for oblong aperture [17] have been reported. Recently, we reported CW-operation green VCSELs [18] with milliwatt class outputs and high-efficiency operation [19] (see Figure 1b). The elimination of the diffraction loss allows an extraordinarily long cavity, which offers other advantages to fabrication stability.…”

“…Figure 1. I-V/L and I-WPE curves of (a) blue [13] and (b) green VCSELs [17] with curved mirror. Insets are emission spectra obtained above threshold currents.…”