Metal-clad Ridge-waveguide Research Articles

A novel dual resonance long period waveguide grating based highly sensitive refractive index sensor with reduced temperature sensitivity

In this paper, we are proposing a novel structure to reduce the temperature cross sensitivity of a refractive index (RI) sensor based on dual resonance long period waveguide grating in a metal clad ridge waveguide, operating near the dispersion turning point. The core of the waveguide is considered to be made of two parts having opposite thermo-optic coefficients with grating written in one part only. Considering the coupling between the fundamental TE mode and a higher order TE mode, we have shown that by adjusting the thickness of the two parts of the core, it is possible to achieve blueshifts for both the resonance wavelengths with the increase in temperature unlike the case of a conventional dual resonance spectrum where two resonance wavelengths show opposite shifts. As a result, an extremely low temperature cross sensitivity ∼0.006 nm/0C has been achieved, whereas the dual resonance spectrum holds its conventional behavior with the change in ambient RI, showing an extremely high RI sensitivity ∼57,260 nm/RIU near water RI 1.33. Further, it has been observed that as we approach the dispersion turning point, temperature sensitivity decreases gradually whereas RI sensitivity increases, leading to a more accurate ambient RI measurement

Highly sensitive temperature sensor based on a long period grating inscribed metal clad ridge waveguide with PDMS surrounding

A highly sensitive temperature sensor based on a long period grating (LPG) written metal clad ridge waveguide (MCRW) with poly-dimethylsiloxane (PDMS) surrounding is proposed and theoretically analyzed. We have exploited the coupling between the fundamental and a higher order quasi-TE mode via the long period grating written in the core of the MCRW. It is shown that owing to the differential enhancement of the two participating modes' evanescent fields in the PDMS surroundings due to the metal under cladding and the high thermo-optic coefficient of PDMS, the thermal dependence of the higher order mode is significantly enhanced as compared to the fundamental mode. In addition, a dispersion turn around behavior in the phase matching graph of the LPG is observed due to the metal under cladding. As a result, a temperature sensitivity as high as ∼100 nm/°C can be achieved by using the dual resonance near the dispersion turning point. Further, due to the highly lossy nature of the quasi-TM modes, no inline polarizer is required to be used with the proposed structure.

Toward 100 Micrometer per Refractive Index Unit Sensitive Sensor Using a Compact Long-Period Grating Inscribed Metal Clad Ridge Waveguide

A novel structure with long-period grating in a metal clad ridge waveguide (MCRW) as a highly sensitive ambient refractive index (ARI) sensor is proposed suitable for biosensing applications. We have exploited the coupling between the fundamental mode and a higher order mode via the long period grating written in the photosensitive core of the MCRW. Utilizing quasi-transverse electric (TE) modes of the MCRW structure, it is shown that ARI sensitivity of ∼ ${{\text{100}}}\,{\mu} {\text{m/}}$ refractive index unit (RIU) can be achieved by using dual resonance near dispersion turn around point. This ultrahigh sensitivity can be attributed to the metal under-cladding which enhances the evanescent field in the ambient medium more prominently for the higher order modes as compared to the fundamental mode. It is shown that device compactness is also increased significantly due to the metal under-cladding. Further, the propagation lengths of quasi-TE modes in the proposed structure are about 35 to 185 times higher than that of quasi-transverse magnetic modes due to which, no in-line polarizer is required in the proposed device.

Metal-clad ridge waveguide structure InGaP/InGaAIP visible laser diodes

InGaP/InGaAIP visible-light laser diodes with a metal-clad ridge waveguide structure have been fabricated. Compressively strained SCH-MQW structures were grown by low-pressure MOCVD and the lasing wavelength was 690 nm. The threshold current was 28 mA at 25°C for a 400 μm cavity and 5 μm stripe width. CW operation was obtained as the cleaved device by employing thick gold layer as a heat spreader. The light-output power versus CW current was linear up to a maximum light output power of 38 mW. Stable operation of the fundamental transverse optical mode was maintained up to 30 mW. These results show that this metal-clad ridge waveguide structure provides sufficient current confinement even under high light output power operation.

Tunable twin‐guide (TTG) laser diodes with metal‐clad ridge‐waveguide (MCRW) structure for coherent optical communications

AbstractTunable twin‐guide (TTG) laser diodes with metal‐clad ridge‐waveguide (MCRW) structure were developed for advanced coherent optical communication systems at 1.55 μm wavelength. The essential advantage of these lasers over previous devices is the simplified handling due to the inherent continuous tuning behaviour enabling the unambiguous wavelength control by only one tuning current. With 400 μm long devices, threshold currents around 50 mA, optical output power levels above 10 mW and tuning ranges around 1.2 nm (150 GHz) are achieved by maintaining the linewidth below 4 MHz. With an optimized design a maximum continuous tuning range of 2 nm has been obtained.

Static and Dynamic Characteristics of Metalorganic-Vapor- Phase-Epitaxy-Grown 1585 nm InGaAs/InGaAlAs Separate Confinement Heterostructure Multiple-Quantum-Well Metal-Clad Ridge-Waveguide Lasers

Fabrication and characteristics of InGaAs/InGaAlAs separate confinement heterostructure multiquantum-well (SCH-MOW) metal-clad ridge-waveguide (MCRW) laser diodes are reported. The layer structures have been grown by atmospheric pressure metalorganic vapor phase epitaxy (AP-MOVPE) without any use of phospine. The lasers emit around 1585 nm, and the minimum cw-threshold current is 15 mA for 200 µm-long lasers with high-reflection (HR) coating on both mirrors. For 600 µm- and 800 µm-long one-side HR-coated devices, continuous wave (CW) output power levels up to 16 mW and CW operation around 60°C have been achieved. A power-limited 3 dB bandwidth of 5.1 GHz has been measured. From small signal modulation measurements, a maximum differential gain of 7.7×10-16 cm2 has been calculated.

Continuously tunable metal-clad ridge-waveguide distributed feedback laser diode

The tunable twin-guide (TTG) structure has been realised with the metal-clad ridge-waveguide (MCRW) distributed feedback (DFB) laser yielding continuous tuning up to 2 nm, output power above 10 mW and linewidth below 10 MHz. The relatively simple fabrication technology and high reliability make this device well suited as a tunable light source for advanced optical communication systems.

Low threshold current MOVPE grown GaInAs-Al(Ga)InAs separate confinement heterostructure multiquantum well metal-clad ridge-waveguide lasers emitting at 1585 nm

GaInAs-Al(Ga)InAs separate confinement heterostructure (SCH) multiquantum-well (MQW) metal-clad ridge-waveguide (MCRW) laser diodes were successfully fabricated for the first time from layer structures grown by atmospheric pressure (AP) metalorganic vapor-phase epitaxy (MOVPE) on InP substrate without any use of phosphine. CW operation of 2.9- mu m-wide and 400- mu m-long MCRW laser diodes emitting at 1585 nm was demonstrated with a minimum threshold current of 38 mA. >

LPE growth and characterization of InP/InGaAsP ridge‐waveguide lasers at 1.3 μm‐wavelength

AbstractThis paper presents the fabrication and the lasing characteristics of 1.3 μm‐wavelength ridge‐waveguide laser. The epitaxial material used in this study was grown applying the step‐cooling technique of liquid phase epitaxy (LPE). The growth conditions for InGaAsP layers lattice‐matched to the (001) InP‐substrate are reported for lattice compositions corresponding to photoluminescence peak wavelengths of 1.07, 1.14, and 1.31 μm. We have used a conventional multiple‐bin sliding boat to grow the LPE layers and a second apparatus for achieving batches of melts of uniform compositions. In the LPE apparatus the various batch melts (In–Sn In–Zn; In–Ga–As of different composition) were saturated with phosphorus using the seed dissolution technique. The epitaxial layers were grown by a single phase technique at a constant temperature. This LPE growth technique is useful for the fabrication of double‐heterostructure wafers with an uniform alloy composition and a well‐defined layer thickness.Using these epitaxial materials, metal‐clad ridge‐waveguide (MCRW) lasers have been prepared with stripe widths of 3.5 μm. CW threshold currents of 18 mA at room temperature are achieved for 200 μm long cavities. These lasers have T0 values ranging from 50 to 70 K and well linear L‐I‐characteristics.

Experimental determination of parasitic optical feedback by diode laser linewidth measurements

Proposes a novel method for the characterisation of parasitic optical feedback by measuring the diode laser linewidth change with injection current. Results were obtained with a MCRW (metal-clad ridge-waveguide) laser and reflections from an optical isolator. A feedback signal 67 dB below the laser output was definitely measured.

Low-threshold, high-power zero-order lateral-mode DQW-SCH metal-clad ridge waveguide (AlGa)As/GaAs lasers

Metal-clad ridge waveguide (MCRW), double quantum well, separately confined heterostrucuture (DQW-SCH) lasers have been fabricated having continuous-wave (CW) threshold currents of 10–12 mA and external differential quantum efficiencies of 41–46% per uncoated facet. Light/current characteristics are linear to >70 mW, and zero-order lateral mode operation was measured at 56 mW. The CW burn-off power density is nearly double the best previously reported value.

Low-Threshold InGaAsP-InP Metal-Clad Ridge-Waveguide (MCRW) Lasers for 1.3 µm Wavelength

Metal-clad ridge-waveguide (MCRW) lasers have been prepared in InGaAsP-InP for 1.3 µm wavelength by liquid-phase epitaxy. CW threshold currents as low as 28 mA and efficiencies above 0.25 mW/mA per facet are achieved. Lasers with 2-3 µm wide stripes show stable operation in the fundamental lateral mode and linear light-current characteristics up to more than 10 mW. The maximum temperature for CW operation of upside-down mounted devices is 75°C.

Calculation of metal-clad ridge-waveguide (MCRW) laser modes by mode coupling technique

The waveguide modes of metal-clad ridge-waveguide (MCRW) lasers are calculated rigorously by way of laterally coupled-mode equations. Thereby propagation constants of the waveguide modes are computed and compared to an approximate theory. Taking into account the complete set of local TE- and TM-eigenmodes, our analysis reveals that MCRW laser modes are mainly TE-polarized with a TM-component of some percent in case of narrow stripe lasers and it is shown that for strong lateral discontinuity of the waveguide geometry radiation losses appear owing to excitation of leaky TM-modes. Furthermore, modes losses caused by metal absorption are investigated and found to be in the order of 10 cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for highly conductive metallizations.

Large Signal Behaviour of Optical Pulse Generation in Q-switched GaAlAs/GaAs Injection Lasers

A large-signal model for passively Q-switched laser structures, consisting of an amplifying and a saturable absorber region, is presented. The amplitude, pulse rate and pulse width of self-sustained pulsations are derived. A comparison with experimental results, obtained from double-contacted metal clad ridge waveguide lasers, is performed.

Design considerations of the metal-clad ridge-waveguide laser with distributed feedback

For the realisation of a distributed feedback (DFB) laser, the properties of a waveguide with a grating adjacent to the laser stripe are investigated. The results are applied to the metal-clad ridge-waveguide (MCRW) structure with DFB grating. It is found that, for small stripe widths, and if the optical field is mainly concentrated within the active region of the waveguide, enough optical feedback may be expected to realise laser operation with efficient longitudinal mode filtering.