Tapping-mode tuning-fork near-field scanning optical microscopy of low power semiconductor lasers

Using ferrule-top opto-mechanical probes as a new tool in VCSEL reliability experiments

Today, vertical cavity surface emitting lasers (VCSELs) are used in many high-end applications, for which the laser lifetime is a critical parameter. Changes in the spatial distribution of the various emission modes of the VCSEL can be used as an early sign of device degradation, enhancing the speed and detail of failure mode analysis. We have developed a ferrule-top combined atomic force microscopy (AFM) and scanning near-field optical microscopy (SNOM) probe that can be used to analyze the transverse mode pattern of the 850 nm radiation at a <200 nm spatial resolution. During accelerated lifetime testing, the newly developed method shows that small local changes in the optical output can already be detected before any sign of device degradation is observed with conventional methods.

DESIGN AND CONSTRUCTION OF A SHORT-TIP TAPPING-MODE TUNING FORK NEAR-FIELD SCANNING OPTICAL MICROSCOPE

The design and construction of a tapping-mode tuning fork with a short fiber probe as the force sensing element for near-field scanning optical microscopy is reported. This type of near-field scanning optical microscopy provides a stable and high Q factor at the tapping frequency of the tuning fork, and thus gives high quality NSOM and AFM images of samples. We present results obtained by using the short tip tapping-mode tuning fork near-field scanning optical microscopy measurements performed on the endfaces of a single mode telecommunication optical fiber and a silica-based buried channel waveguide.

Implementation of a short-tip tapping-mode tuning fork near-field scanning optical microscope

We present the implementation of a short-tip tapping-mode tuning fork near-field scanning optical microscope. Tapping frequency dependences of the piezoelectric signal amplitudes for a bare tuning fork fixed on the ceramic plate, a short-tip tapping-mode tuning fork scheme and an ordinary tapping-mode tuning fork configuration with an 80-cm optical fibre attached are demonstrated and compared. Our experimental results show that this new short-tip tapping-mode tuning fork scheme provides a stable and high Q factor at the tapping frequency of the tuning fork and will be very helpful when long optical fibre probes have to be used in an experiment. Both collection and excitation modes of short-tip tapping-mode tuning fork near-field scanning optical microscope are applied to study the near-field optical properties of a single-mode telecommunication optical fibre and a green InGaN/GaN multiquantum well light-emitting diode.