Chinese Optics, Volume. 16, Issue 5, 1177(2023)
Method for the simultaneous measurement of waveguide propagation loss and bending loss
Fig. 1. Process flow of LN waveguide fabrication. (a) LNOI substrate. (b) Deposition of oxide by PECVD. (c) I-line lithography. (d) Hard mask etching. (e) LN etching. (f) Photoresist removal. (g) Hard mask removal. (h) Deposition of cladding by PECVD
Fig. 4. Layout image of the 5 sets of cutback structures for the 5 splits of the grating coupler
Fig. 5. (a) Simulation of the bending loss of the LN waveguide. The bending loss of the waveguide is exponentially related to the bending radius. (b) The linear fitting of the natural logarithm of the bending loss with the bending radius
Fig. 7. The measurement results of the cut-back structure and the fitting results. (a) GC1, (b) GC2, (c) GC3, (d) GC4, (e) GC5-1, (f) GC5-2
Table 1. The basic information of the cut-back structure
View tableView in ArticleTable 1. The basic information of the cut-back structure
Length(cm) The radius of bend(μm) Number of radius WG1 0.1582 100, 110 100×4,110×2 WG2 0.9021 100,110,120,130,140,150 (100-140)×4,150×2 WG3 2.2054 100,110,120…190,200 (100-190) ×4,200×2 WG4 5.2274 100,110,120…290,300 (100-290) ×4,300×2 WG5 11.4854 100,110,120…490,500 (100-490) ×4,500×2
Table 2. The summary of the fitting results
View tableView in ArticleTable 2. The summary of the fitting results
α(dB/cm) αb0(dB） k αgc(dB) r GC1 0.538 0.805 0.0446 20.220 0.072 GC2 0.408 0.698 0.0346 15.448 0.261 GC3 0.558 0.698 0.0399 10.740 0.044 GC4 0.209 0.393 0.0201 12.114 0.366 GC5-1 0.194 0.416 0.0176 35.350 0.355 GC5-2 0.421 0.339 0.0194 29.666 0.230
Table 3. The performance comparison of different measurement methods
View tableView in ArticleTable 3. The performance comparison of different measurement methods
Advantages Disadvantages Traditional cut-back[ 33 ]Widely employed owing to its ease of use. Can’t simultaneously measure the propagation loss and bending loss; Requires identical coupling conditions. Three-prism Method[ 34 ]Does not require constant coupling conditions Has low measurement accuracy. Fabry-Perot transmission method[ 35 ]Can eliminate the influence of coupling loss and has higher accuracy Requires a complex coupling system. This paper Can simultaneously measure waveguide propagation loss and bending loss; Smaller footprint; Simple and convenient operation.
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Zuo-wen FAN, Lian-xi JIA, Zhao-yi LI, Jing-jie ZHOU, Qing-yu CONG, Xian-feng ZENG. Method for the simultaneous measurement of waveguide propagation loss and bending loss[J]. Chinese Optics, 2023, 16(5): 1177
Category: Original Article
Received: Nov. 27, 2022
Accepted: --
Published Online: Oct. 27, 2023
The Author Email: Lian-xi JIA (jialx@mail.sim.ac.cn)
