Nowadays novel micro-fabrication and wafer-based manufacturing approach allows realizing micro-optics in a way
scientists have dreamt for generations, in particular, utilizing nano-imprint lithography as fabrication tooling enables
greatly accelerating the micro-optics technology to its frontier. In this report, we present wafer-scale fabrication of
various types of micro-optical elements based on photoresist, benzocyclobutene, photocurable imprint resist, and
semiconductor materials by using thermal reflow, reactive ion etching, and imprint techniques. Especially, several
concave or convex 3-dimensional micro-optical structures shaped by imprint method are detailed. These micro-optical
elements can be monolithically or hybrid integrated onto optoelectronics devices, such as photodetectors and emitters as
optical beam focuser, collimator, filter, or anti-reflectance elements. As application examples, polymer microlenses were
integrated directly on the top of UV dual functional devices and quantum dot long wavelength infrared photodetectors,
respectively.
A high-power single-mode 1.3-μm InGaAs/GaAs vertical-cavity surface-emitting laser (VCSEL)
structure employing a novel concept of engineering the optical mode profile to match the gain profile is
suggested and demonstrated experimentally and theoretically. In contrast to various singlemode
VCSEL approaches reported in the literature so far, based on selective loss or anti-resonant effects to
suppress higher order modes, it is due to a novel design to increase the active region size while
maintaining single mode emission. The shape of the fundamental mode profile is engineered to be
similar to the gain profile which resembles a doughnut shape especially in intra-cavity contacted
devices. In this way, the fundamental mode with the best fit to the gain profile can reach the lasing
condition earliest and consume all the optical gain, leading to a suppression of higher order modes.
Notably, despite this engineered shape of the mode profile, the far field shape remains close to
Gaussian. The mode shaping can be achieved by introducing a shallow intracavity patterning before
depositing the top mirror. Fabricated device structures consist of a A-Si/SiN/SiO2 top mirror,
modulation-doped current spreading layers, re-grown current confinement layers, three InGaAs/GaAs
quantum wells, and a GaAs/AlGaAs bottom mirror. Single mode operation is demonstrated even for
devices with active region as large as 10μm.
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