1.3 μm InGaAlAs asymmetric corrugation‐pitch‐modulated DFB lasers with high mask margin at 28 Gbit/s

Abstract

Direct modulation of a 1.3 µm InGaAlAs asymmetric corrugationpitch-modulated (ACPM) distributed feedback (DFB) laser operated at 28 Gbit/s was experimentally demonstrated. The laser exhibits linear light-current characteristics and a high-frequency response with a small roll-off at low frequency compared with a conventional λ/4-shifted DFB laser. Moreover, it attains a high mask margin (20%) under 28 Gbit/s operation at 55°C. These superior properties are due to a superior ACPM grating that suppresses longitudinal spatial hole-burning.Introduction: With the explosive growth of Internet/Intranet traffic, high-speed optical transceivers for 100 GbE should reduce power consumption and module sizes. High-speed directly modulated lasers are attracting attention as light sources to meet these demands because this type of light source has low power consumption and a small footprint. There have been some reports on the 25 Gbit/s operation of directly modulated lasers [1][2][3][4]. However, only a few results on 28 Gbit/s directly modulated lasers have been reported [5]. Operation at 28 Gbit/s is important for transmitting data with the OTU4 frame format.We recently reported 28 Gbit/s directly modulated DFB lasers with an asymmetric corrugation-pitch-modulated (ACPM) grating [6]. In this Letter, the static and dynamic properties of the ACPM distributed feedback (DFB) laser are investigated through comparison with a quarterwavelength (λ/4)-shifted DFB laser. The ACPM grating suppresses the longitudinal spatial hole-burning [7]. It is experimentally demonstrated that ACPM DFB lasers have linear light-current characteristics and a high-frequency response with small roll-off at low frequency, compared with the conventional λ/4-shifted DFB lasers. This superior frequency response of the ACPM lasers enables 28 Gbit/s operation with a high mask margin (MM) of 20% at 55°C.

Direct Modulation at 56 and 50 Gb/s of 1.3-<inline-formula> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula>m InGaAlAs Ridge-Shaped-BH DFB Lasers

“…These values of the threshold current are the lowest values among those of high-speed edge-emitting lasers operating above 20 Gb/s so far reported, to our knowledge. The measured series resistance was 10 , which is comparable to that of the 25 and 28-Gb/s lasers [9]- [12].…”

“…As described in ref. 12, the ACPM DFB laser has smaller roll-off value than the conventional quarter-wavelength-shifted DFB laser. The CPM laser was proposed to suppress longitudinal spatial hole-burning [13].…”

“…The epitaxial layers of the device were grown on an n-InP substrate by low-pressure metal-organic chemical vapor deposition (LP-MOCVD). The active layer consists of undoped InGaAlAs MQW and SCHs layers, which are the same as those of 25-Gb/s and 28-Gb/s lasers [9]- [12]. The current blocking layers that consist of a semi-insulated semiconductor are buried adjacently on both the sides of the grating, the MQW with SCHs, and n-InP cladding layers.…”

Uncooled 100-GBaud Directly Modulated Membrane Lasers on SiC Substrate

“…We fabricated a lateral p-i-n structure that enabled lateral current injection, which has the advantage of reducing the RC time constant by reducing the pad-electrode capacitances. We formed uniform gratings on the InP surface, because they can avoid spatial localization of the optical power distribution (i.e., the spatial hole burning effect), in contrast to λ/4-shifted gratings [25]. The grating coupling coefficient was designed to be 600 cm -1 , giving a photon lifetime of ~1 ps.…”