| In recent years many new measuring techniques have been developed, Such as light emission technique,electron beam measuring technique,photoconductionsampling technique and so on. An excellent measuring technique for electric signals should have excellent temporal resolution, spatial resolution and voltage sensitivity. Such as electro-optic sampling, a continuous wave electro-optic detecting system and so on. Electro-optic measuring technique is a promising technique based on Pockels effect. The technique combines with optics, laser technique, electronics, sampling technique and so on, using super-short laser to measure the internal characteristic in electric devices The voltage sensitivity of the electro-optic measuring technique is very High as well, usually below .While the spatial resolution of the electro-optic measuring technique is usually determined by the minimum spot size of the probing laser beam. For 1.3μm light source, the spatial resolution was about 3μm. According to the Abbe's theory of diffraction, the spatial resolution is limited the micron level, which is not suitable for probing ultra-high density electronic devices and circuits with sub-micron configures. The article studied that the electro-optic measuring technique combined with solid immersion lens technique, increased the effective numerical aperture and decreased the spot size to sub-micron level. Generally, the full-width at half maximum (FWHM) of the minimum focused spot size of the probing laser beam is defined as the spatial resolution of the electro-optic measuring technique. The FWHM of the focused spot can be written as .Where the , is the number aperture of the microscopy objective. Here, θis the angle between the outermost rays and the optic axis. n is the refractive index of the object space. λ is the wavelength in the vacuum of the probing beam. From here we can see that there are two methods to decrease the spot size and increase the spatial resolution: decreasing the wavelength of the probing beam and increasing the effective numerical aperture of the focusing system. If selected the short wavelength probing beam, wide forbidden area electro-optic materials such as KDP,ZnTe,GaP should be considered. But the wavelength can not be infinity short. At the same time, for some electro-optic crystal, the wavelength of the probing beam should be longer than absorbability wavelength. Otherwise bringing to essence absorbing, losing light energy, which will induce to the damage of devices.Increasing the effective numerical aperture of the focusing system, This can be realized by using the solid immersion lens (SIL) which principle is similar to the liquid immersion lens. We selected semi-insulation GaAs to make a super-hemisphere electro-optic solid immersion probe (EOSIP). In experiments, GaAs super-hemisphere is used as not only the SIL, but also the electro-optic probe. Applying the super-hemisphere GaAs EOSIP, we measured sinusoidal signals propagating on the ceramic microstrip (MSL) successfully. The EO signals were displayed on the lock-in amplifier, and the wave forms of the output signal can be observed with an oscilloscope, and under the same measuring conditions we detected the electric field of the same sample with a GaAs hemisphere EOSIP. The results indicate that the voltage sensitivity was also increased by a factor of about 3.7 in contrast with a hemisphere. The increment of voltage sensitivity has been analyzed by the reflective power calculation of the GaAs hemisphere and super-hemisphere. Compared with hemisphere, the reflective power was increased about 5.23 times using a GaAs super-hemisphere. The focused spot size was measured respectively using GaAs hemisphere and super-hemisphere. Compared with GaAs hemisphere, the spot size was decreased about 2.8 times by GaAs super-hemisphere. So the spatial resolution was improved further. The theoretical spatial resolution was 0.29μm by a super-hemisphere, and it was 3.4 times as much as a hemisphere. At the same time maximal numerical aperture can b...
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