Frank Riemenschneider

Continuously tunable long-wavelength MEMS-VCSEL with over 40-nm tuning range

This letter presents for the first time an electrically pumped tunable vertical-cavity surface-emitting laser (VCSEL) with a record-breaking tuning range of 40 nm at long wavelengths. The VCSEL is based on a two-chip concept. The laser peak can be tuned continuously and without mode-hopping in a wavelength range above 1.55 /spl mu/m due to a microelectromechanical movable mirror membrane. The VCSEL is single mode all over the tuning range with a 32-dB sidemode suppression ratio. The laser emits a maximum output power of 100 /spl mu/W in continuous-wave operation at room temperature. Dynamic measurements of the tuning characteristics show that the 3-dB cutoff frequency for an electrothermal wavelength modulation is about 500 Hz and the 1/e-time constant of the step response is about 1 ms.

Low-cost electrothermally tunable optical microcavities based on GaAs

In this letter, we present a new simple and, therefore, low-cost two-chip concept for the fabrication of electrothermally tunable optical microcavities. Those microcavities will be applicable to tunable components for wavelength-division multiplexing systems, such as tunable filters and tunable lasers. The performance of such a microcavity is demonstrated by fabricating a tunable filter that is based on the proposed concept.

A new concept for tunable long wavelength VCSEL

Abstract We present a novel two-chip concept for micro-electro-mechanically tunable vertical cavity surface emitting lasers (VCSELs) for the 1.55 μm wavelength range. The VCSEL is composed of two chips: one mirror membrane chip with a movable curved mirror membrane that can be displaced by electro-thermal actuation to adjust the cavity length and one “half-VCSEL” chip consisting of a fixed bottom mirror and an amplifying active region. The possibility of separate optimization of the micro-mechanical part and the VCSEL amplifier is the main advantage of that concept, which is appropriate for photo-pumping as well as for an electrical pumping scheme. The measurement results of an optically pumped VCSEL with more than 0.5 mW continuous wave (CW) single mode output power at room temperature over a 24 nm tuning range prove the feasibility of the proposed concept.

Bulk-Micromachined VCSEL At 1.55

A single-mode continuous tuning range of 76 nm is realized using a bulk-micromachined vertical-cavity surface-emitting laser (VCSEL) operating at wavelengths around 1.55 mum. The bulk-micromachined upper mirror is optimized for dielectric material and manufactured separately from the half-VCSEL. The VCSEL is tuned by an electrothermal actuation of a concave bended membrane. The tuning range characteristics in dependence on the bias of the VCSEL are investigated. It is determined that the tuning range saturates by increasing the current of the VCSEL and a further increase causes a multimode behavior within the tuning range.

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This paper studies the effects of microforces on micromachined active Fabry-Peacuterot laser cavities. A simple mechanical model is established to analyze the influence of these microforces on the microelectromechanical system (MEMS)-realization of the Bragg mirrors inside a microcavity. The presence of thermal noise of the MEMS structure directly influences the linewidth and wavelength stability of MEMS lasers. Other microforces, such as radiation pressure, radiometric pressure, and length extension due to thermal heating also determine the wavelength stability during dynamic operation, leading to a micromechanic chirp component. The theoretical analysis is compared directly with the experimental data obtained from measurements with a MEMS vertical-cavity surface-emitting laser (MEMS-VCSEL). The results are in agreement with the data predicted by the modeling and prove the viability of the approach

m With 76-nm Single-Mode Continuous Tuning Range

This letter analyzes the influence of micromachined Bragg mirrors within active Fabry-Perot cavities on basic laser characteristics, like linewidth and chirp. The impact of thermal noise of the micromechanic structure is discussed and its influence on the linewidth of a microelectromechanical system (MEMS)-tunable vertical-cavity surface-emitting laser (VCSEL) is verified in an experiment. For the first time, we demonstrate for a MEMS-VCSEL a record low average linewidth of 210 MHz and extract an intrinsic linewidth of below 30 MHz. The second issue deals with the influence of microforces like radiation pressure, radiometric pressure, and length extension of the Bragg-mirror structure due to absorption on the chirp behavior of a MEMS-laser. For the first time, these effects and their influence on the VCSEL dynamics are modelled and discussed in detail. Further, the measured chirp characteristics are analyzed and compared with our modelling to quantify the influence of above effects on the device characteristics

Impact of Micromechanics on the Linewidth and Chirp Performance of MEMS-VCSELs

Wavelength Division Multiplexing has become a leading technology for long haul transmission systems which operate at 1550 nm wavelength. One of the key components of such systems are tunable filters. Beside low insertion loss, polarisation insensitivity and large tuning range there is a strong demand for cost effectiveness and reliability. Two-chip micromachined filters are very promising candidates to fulfil these demands. In this paper we present and discuss a tunable optical filter structure which uses a simple bulk-micromachining process based on low-cost dielectric Bragg mirrors. The tuning is achieved by current induced thermal heating of the membrane suspensions. Common micromachined tunable optical filters either employ semiconductor Bragg mirrors with current induced heating or dielectric membrane mirrors with electrostatic actuation. The new concept combines the advantages of both types, the low-cost dielectric material and the simple actuation principle by current flow to create a best-of-breed two-chip solution. The alignment process of the two-chip cavity has been simplified to the point where a simple place-and-fix strategy can be applied. By matching the exciting Gaussian input beam to the stable half-symmetric cavity a fiber coupled and packaged tunable optical filter has been realized based on this concept. These micromachined tunable membranes are in general applicable to a wide variety of tunable components for wavelength division multiplexing systems, such as tunable optical filters, receivers and vertical cavity surface emitting lasers (VCSEL).

Linewidth and Chirp of MEMS-VCSELs

The design and characterization of bulk micro-machined tunable VCSELs operating at 1.5 mum are presented. Tuning ranges of more than 20 nm with side mode suppression larger than 40 dB and output powers larger 2 mW were obtained

Micromachined two-chip, low-cost tunable filters for WDM

Singlemode emission exceeding 1 mW over 28 nm tuning range of an electrically pumped long-wavelength VCSEL is achieved. A tunable curved MEMS Bragg mirror enables high output power operation with sidemode suppression of more than 40 dB

Tunable long-wavelength VCSELs using a moveable mirror membrane

This letter presents for the first time the dynamic characteristics of a tunable optically pumped 1.6-/spl mu/m vertical-cavity surface-emitting laser (VCSEL) based on micromechanic wavelength tuning. The study includes analysis of the small-signal amplitude modulation response, the relative intensity noise, and the influence of different pump lasers on the VCSEL noise. From the measurements, characteristic semiconductor parameters have been derived and are presented.