Interferometric microscale measurement of refractive index at VIS and IR wavelengths

Determination of refractive index of micro-disks of a calcinated ( 1100^\circ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mn>1100</mml:mn> <mml:mo>∘</mml:mo> </mml:msup> </mml:math> C in air) photo-resist SZ2080 ^\mathrm{TM} <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:msup> <mml:mi/> <mml:mstyle mathvariant="normal"> <mml:mi>T</mml:mi> <mml:mi>M</mml:mi> </mml:mstyle> </mml:msup> </mml:math> was carried out using transmission and reflection spectroscopy. Interference fringes at specific wavenumbers/wavelengths were selected for determination of the optical thickness, hence, the refractive index when the thickness of micro-disks was measured by scanning electron microscopy (SEM). Refractive index of disks of \sim 6± 1~\mu <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mo>∼</mml:mo> <mml:mn>6</mml:mn> <mml:mo>±</mml:mo> <mml:mn>1</mml:mn> <mml:mspace width="0.222em"/> <mml:mi>μ</mml:mi> </mml:mrow> </mml:math> m thickness were determined at visible and IR (2.5-13~ \mu <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mi>μ</mml:mi> </mml:math> m) spectral ranges and where 2.2± 0.2 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"> <mml:mrow> <mml:mn>2.2</mml:mn> <mml:mo>±</mml:mo> <mml:mn>0.2</mml:mn> </mml:mrow> </mml:math> at visible and IR wavelengths. Peculiarities of optical characterisation of micro-optical structures are discussed in view of possible uncertainties in the definition of geometric parameters, shape and mass density redistribution.