The design, fabrication and characterization of a fundamental/first-order mode converter based on mul- timode interference coupler on InP substrate were reported. Detailed optimization of the device parameters were investigated using 3D beam propagation method. In the experiments, the fabricated mode converter realized mode conversion from the fundamental mode to the first-order mode in the wavelength range of 1530-1565 nm with ex- cess loss less than 3 dB. Moreover, LPol and LP11 fiber modes were successfully excited from a few-mode fiber by using the device. This InP-based mode converter can be a possible candidate for integrated transceivers for future mode-division multiplexing system.
Transverse mode characteristics of a laser are related to a variety of interesting applications. An on-demand mode solid laser in the 1064 nm band was proposed previously. In this paper, we provide a fiber laser for on-demand modes in the 1550 nm band to prescribe the pure and high-quality emission of a higher-order transverse laser mode, based on a simple construction with one spatial light modulator(SLM) and a single-mode erbium-doped fiber(SM-EDF). The SLM is designated to generate the desired higher-order mode and separate the higher-order mode and the fundamental mode. The fundamental mode oscillates in the fiber ring laser, and therefore the SM-EDF can be pumped with a single-mode 980 nm laser, no matter what higher-order mode is prescribed.In this proof-of-principle experiment, high-quality higher-order modes are observed from LP01 to LP105.Stable emission and real-time switching between modes can be easily realized by altering the phase on the SLM. In addition, the propagation of the LP_(01), LP_(11), LP_(21), and LP_(02) modes from the fiber laser is also demonstrated in a four-mode few-mode fiber.
A monolithic integrated few-mode transmitter comprising of two directly modulated distributed feedback lasers and a multimode-interference-coupler-based mode converter-multiplexer with 66% mode conversion efficiency was designed and demonstrated. A fundamental TE0 mode and a first-order TE1 mode were successfully generated from the transmitter, with the output power of 4 and 5.5 mW at a pump current of around 150 mA, respectively,at the common output port. The small signal modulation bandwidth of the TE0 and TE1 channels reached 17.4 and 14.7 GHz, respectively. Error-free 2 × 10-Gbit∕s direct modulation of the two-mode transmitter was demonstrated, with a power penalty of 4.3 dB between the TE0 mode and the TE1 mode at the bit error rate of 1 × 10^(-9).
ZHAOSONG LIDAN LuYIMING HEFANGYUAN MENGXULIANG ZHOUJIAOQING PAN
An In P-based monolithically integrated few-mode transmitter aiming at the combination of wavelength division multiplexing（WDM） and mode division multiplexing（MDM） technologies is proposed. The core elements of the proposed transmitter are mode converters and a wavelength-mode division multiplexer that are all based on multimode interference（MMI） couplers. Simulations show that the wavelength-mode division multiplexer has a large fabrication tolerance of 30 and 0.5 μm for the length and the width of the device, respectively.A low loss below 0.26 dB for the passive parts of the transmitter is obtained in the whole C-band wavelength range.
