High modulation efficiency and large bandwidth thin-film lithium niobate modulator for visible light

Abstract

We experimentally demonstrate an integrated visible light modulator at 532 nm on the thin-film lithium niobate platform. The waveguides on such platform feature a propagation loss of 2.2 dB/mm while a grating for fiber interface has a coupling loss of 5 dB. Our fabricated modulator demonstrates a low voltage-length product of 1.1 V·cm and a large electro-optic bandwidth with a roll-off of -1.59 dB at 25 GHz for a length of 3.3 mm. This device offers a compact and large bandwidth solution to the challenge of integrated visible wavelength modulation in lithium niobate and paves the way for future small-form-factor integrated systems at visible wavelengths.

Sub-1 Volt and high-bandwidth visible to near-infrared electro-optic modulators

“…d Comparison of modulator figure of merit BW/ V π between this work, state-of-the-art commercial LN modulators, previous VNIR thin-film LN modulators, and other VNIR modulator platforms. This work exhibits significantly higher BW/ V π values than all previously reported works, including previously demonstrated TFLN VNIR modulators 30 -- 32 , 37 . The dashed lines correspond to constant values of BW/ V π .…”

“…The increase in V π L for longer wavelengths follows from the smaller phase accumulation for the same modulator length. Our V π L is a factor of 2-3 smaller, depending on wavelength considered, than the best previously reported values for VNIR TFLN modulators, without compromising bandwidth or device insertion loss [30][31][32] . We note that our improvement stems predominantly from the reduction in electrode gap, i.e., enhancement in optical-microwave field overlap.…”

“…A variety of visible integrated photonic platforms have been demonstrated, including silicon nitride 2 , 22 – 25 , aluminum ntiride 26 , 27 , diamond 28 , 29 , and lithium niobate (LN) 30 – 32 . LN is particularly compelling due to its large electro-optic (EO) coefficient, low optical loss, and wide transparency window, making it the workhorse material for the modern day telecommunications industry.…”

“…For example, visible integrated photonic platforms can be combined with any of the large variety of atomic or atomic-like systems with transitions in the VNIR such as alkali and alkaline-earth metal atoms 8-10 , rare-earth ions 11 , diamond color centers 12,13 and quantum dots [14][15][16] . Concerning quantum applications, VNIR photonics enables photon routing 17,18 , spectral shifting for interfacing disparate quantum emitters 11,19 , or realizing higher-dimensional encoded quantum states 20,21 , all in a scalable and compact approach.A variety of visible integrated photonic platforms have been demonstrated, including silicon nitride 2,22-25 , aluminum ntiride 26,27 , diamond 28,29 , and lithium niobate (LN) [30][31][32] . LN is particularly compelling due to its large electro-optic (EO) coefficient, low optical loss, and wide transparency window, making it the workhorse material for the…”

“…Beyond the inherent miniaturization and integratability achievable with TFLN, the strong optical confinement and increased tailorability have enabled performance not achievable with bulk LN, including CMOS compatible drive voltages and high bandwidth operation [34][35][36] . As a result of LN's large transparency window, EO TFLN devices in the visible regime have been demonstrated [30][31][32] . However, half-wave voltages (V π ) and large bandwidths beyond that realized in visible bulk devices has yet to be demonstrated in VNIR TFLN.…”