GHz Broadband SH0 Mode Lithium Niobate Acoustic Delay Lines

Abstract

We present the first group of GHz broadband SH0 mode acoustic delay lines (ADLs). The implemented ADLs adopt unidirectional transducer designs in a suspended X-cut lithium niobate thin film. The design space of the SH0 mode ADLs at GHz is first theoretically investigated, showing that the large coupling and sufficient spectral clearance to adjacent modes collectively enable the broadband performance of SH0 delay lines. The fabricated devices show 3-dB fractional bandwidth ranging from 4% to 34.3% insertion loss between 3.4 and 11.3 dB. Multiple delay lines have been demonstrated with center frequencies from 0.7 to 1.2 GHz, showing great frequency scalability. The propagation characteristics of SH0 in lithium niobate thin film are experimentally extracted. The demonstrated ADLs can potentially facilitate broadband signal processing applications.

5-GHz Antisymmetric Mode Acoustic Delay Lines in Lithium Niobate Thin Film

“…Third, large k 2 above 5 GHz can overcome conventionally unforgiving trades between IL and FBW [34], consequently allowing lowloss and wide-band signal processing functions. For example, up to 30% FBW is accessible without significantly increasing IL at 5.5 GHz (k 2 of 15%) [42].…”

“…Comparing the performance between ADLs from different groups, devices with larger cell lengths have lower center frequencies. However, unlike S0 and SH0 [42], [44], the A1 center frequency does not scale inversely to the cell length due to the dispersive nature of A1. Moreover, higher frequency devices tend to have flatter group delays in the passband, which are consistent with Fig.…”

“…Compared with ADLs on other piezoelectric thin films [48]- [51], these demonstrations feature lower IL and larger FBW due to the simultaneously high k 2 and low damping of S0 [52], [53] and SH0 [54]- [56] modes in LiNbO3. Nevertheless, it remains challenging to scale them above 3 GHz without resorting to narrow electrodes and ultra-thin films (<300 nm) [44], which are undesirable in terms of fabrication complexity and mostly lead to spurious modes that limit the achievable FBW [42]. Therefore, a new piezoelectric platform with simultaneously high vp, large k 2 , and low-loss is sought after for potential eMBB applications.…”

Low-Loss 5-GHz First-Order Antisymmetric Mode Acoustic Delay Lines in Thin-Film Lithium Niobate

“…The obtained results (Baseline and Group B) are compared with the previously reported ADLs [22]- [27], [29], [30], [32], in Fig. 16 and Table III.…”

“…In this article, we have included a detailed analysis of unidirectional transducer design, piezoelectric substrate orientation selection, and key design parameters. Compared to the state-of-the-art ADLs with similar feature sizes, this article presents a substantial enhancement in both the IL (4.9 dB less) [32] and operating frequency (3 times higher) [26], [27], [29], [30]. It is organized as follows.…”