Byoung Joo Kim

Speckle noise reduction on a laser projection display via a broadband green light source

A broadband green light source was demonstrated using a tandem-poled lithium niobate (TPLN) crystal. The measured wavelength and temperature bandwidth were 6.5 nm and 100 °C, respectively, spectral bandwidth was 36 times broader than the periodically poled case. Although the conversion efficiency was smaller than in the periodic case, the TPLN device had a good figure of merit owing to the extremely large bandwidth for wavelength and temperature. The developed broadband green light source exhibited speckle noise approximately one-seventh of that in the conventional approach for a laser projection display.

Nondestructive quality evaluation of periodically poled lithium niobate crystals by diffraction

We derived an expression for the noise between the diffraction orders from a random grating. The result was applied to analyze the statistical duty-cycle error in PPLN, providing an efficient means for poling quality evaluation.

Evaluation of domain randomness in periodically poled lithium niobate by diffraction noise measurement

Random duty-cycle errors (RDE) in ferroelectric quasi-phase-matching (QPM) devices not only affect the frequency conversion efficiency, but also generate non-phase-matched parasitic noise that can be detrimental to some applications. We demonstrate an accurate but simple method for measuring the RDE in periodically poled lithium niobate. Due to the equivalence between the undepleted harmonic generation spectrum and the diffraction pattern from the QPM grating, we employed linear diffraction measurement which is much simpler than tunable harmonic generation experiments [J. S. Pelc, et al., Opt. Lett.36, 864-866 (2011)]. As a result, we could relate the RDE for the QPM device to the relative noise intensity between the diffraction orders.

Estimation of random duty-cycle error in periodically poled lithium niobate by simple diffraction experiment

Random duty-cycle errors (RDE) in ferroelectric quasi-phase-matching (QPM) devices not only affect the frequency conversion efficiency, but also generate non-phase-matched background noise. Although such noise contribution can be evaluated by measuring second-harmonic generation (SHG) spectrum with tunable narrow-band lasers, the limited tuning ranges usually results in inaccurate measurement of pure noise. Instead of SHG, we took a diffraction pattern which is mathematically equivalent to the SHG spectrum, but can be obtained with greater simplicity. With our proposed method applied to periodically poled lithium niobate, RDE could be evaluated more accurately from the pure background noise measurement.

Development of efficient broadband green light source by tandem quasi-phase-matched structure

Broadband green light source using a 5.5-mm-long tandem PPLN was demonstrated. The measured wavelength and temperature bandwidth were 13nm and 100°C, respectively, which had 34.2 times broader spectral bandwidth than periodic one.

Fabrication of maskless quasi-phase matching device

We report a laser writing system for fabrication of maskless QPM devices with violet laser diode module. Maskless QPM devices with periods 50 μm and 27 μm were successfully poled by standard electric field poling technique.

Direct Bonding of Periodically-Poled Lithium Niobate Crystals for Slanted Quasi-Phase Matching

We fabricated a thick periodically-poled lithium niobate (PPLN) by direct bonding two PPLNs. With a fundamental beam propagating at 23 deg. from x-axis, we observed simultaneous quasi-phase-matching of the second and third-harmonic generations.

Nondestructive quality evaluation of periodically poled lithium niobate crystals by diffraction-noise measurement

We derived an expression for the noise between the diffraction orders from a random grating. The result was applied to analyze the statistical duty-cycle error in PPLN, providing an efficient means for poling quality evaluation.

Analysis of periodically poled domains of lithium niobate crystal by diffraction

We demonstrate an efficient far-field diffraction method for quality assessment of periodically poled lithium niobate crystals. Microscopic and macroscopic analyses are carried out to obtain important statistical quantities and to assess the final device performance.

Ultra-broadband optical parametric generation in periodically poled lithium niobate and stoichiometric lithium tantalate crystals

We report ultra-broad optical parametric gain spectra centered at near infrared in periodically poled congruent LiNbO3 and stoichiometric LiTaO3 crystals, using group-velocity matching near the degeneracy point. They can be useful for ultra-fast pulse applications.