Figure
1.
(a) The simulation model; (b) schematic diagram of simplified facet; (c) schematic diagram of asymmetric structure; (d) linear and parabolic refractive index distributions
| Citation: | YOU Dao-ming, TAN Man-qing, GUO Wen-tao, CAO Ying-chun, WANG Zi-jie, YANG Qiu-rui, WAN Li-li, WANG Xin, LIU Heng. Design and fabrication of an optical film for fiber bragg grating external cavity diode lasers[J]. Chinese Optics, 2023, 16(2): 447-457. doi: 10.37188/CO.EN.2022-0010
|
The cavity surface optical film is one of the most crucial components of the fiber bragg grating External Cavity diode Laser (ECL). Although, the Plane Wave Method (PWM) is widely used in the optical film preparation, it is not an ideal design method when applied in ECL preparation. The Finite-Difference Time-Domain (FDTD) method is used to analyze this problem by taking the effect of facet dimensions and structure into account. According to the simulation, PWM suffers from poor reflectivity and deviation of the reflection curve, which significantly affects performance. Therefore, the optical film design is optimized and verified by experiments. Magnetron sputtering is used to fabricate the optical film, which is then applied to ECL. The measurement results show that the reflectivity of Anti-Reflection (AR) film is reduced by 30% after optimization, while the reflectivity of High-Reflection (HR) film increased to 96%. The prepared ECL’s fiber output power exceeds 650 mW. In this paper, the optical film suitable for ECL is designed and fabricated, and provides a reference for optical films in ECLs and other semiconductor optoelectronic devices.
The External Cavity diode Laser (ECL) has the advantages of narrow linewidth, high reliability, and long service life, so it is widely used in the field of optical sensing and communication[1]. Facet reflection is the key feature of ECL, which modifies the optical field distribution by altering feedback intensity, and is closely related to the mode and optical catastrophe threshold[2-3].
As ECL gains popularity, problems arise. Internal cavity loss, brought on by mode hopping from lingering front facet reflections, is one of the most urgent problems because it directly affects characteristics such as power and spectrum, which is not suitable for communications and especially tunable applications[4]. Additionally, the rear facet typically calls for high reflectivity to maintain high power. Therefore, ECL has strict requirements for the optical film on facet reflection. The optical film is fabricated on the facet of the Laser Diode (LD) in ECL. The reflectivity of HR film must be more than 95%, and the reflectivity of AR film must be less than 1% or even be 0.1%[5-6].
Conventional optical film is designed by the Plane Wave Method (PWM), which is used for laser coating[7-8]. A large-scale plane will benefit more from this design, because it is based on the Fresnel formula and transfer matrix. However, when PWM-designed films are used in ECL preparation, the actual performance is found to be far from its theoratical design results[9], resulting from the LD facet’s extremely small size and complex structure. PWM is unable to handle this challenging condition. Previous studies mainly consider two-dimensional conditions and ignored many important influential factors[10]. Therefore, analyzing optical film design by using more accurate methods and models that are more consistent with real devices is of great interest to ECLs.
To analyze the reflective properties of optical films on tiny and intricate surfaces, previous researchers have already proposed plane wave expansion, the Free Space Radiation Mode (FRSM), and the Finite Difference Time Domain (FDTD)[11-12], among which FDTD shows the most superior accuracy[13-19]. Film optimization is additionally hampered by the difficulty of directly measuring reflectivity due to its size restrictions. As a result, the indirect measuring approach has replaced other methods for reflectivity measurement in LD, and optical films are optimized using genetic algorithms and particle swarm.
To design and fabricate high-performance optical films for ECLs. The simulation and experimentation methods are explained in Section 2. The results of the simulation are analyzed and design is optimized in the following section. Section 4 discusses the application of optimized films to ECLs after their experimental validation. The final section provides a summary of the entire study.
We used FDTD, a numerical solution to Maxwell’s equation, to accurately simulate the optical film on the facet. It is based on the theory that the electric and magnetic fields are alternately sampled in space and time. The foundation of FDTD is to expand Maxwell's spinodal equations[20]:
| ∇×→H=∂→D∂t+→Jm, | (1) |
| ∇×→E=−∂˙B∂t−→Jm, | (2) |
where
| f(x,y,z,t)=f(iΔx,iΔy,jΔz,kΔx,nΔt)=fn(i,j,k). | (3) |
Then, solving the first-order partial differential equations for each lattice point by obtaining an approximate solution of the central difference equation results in:
| {∂f∂x|x=iΔx≈1Δx[fn(i+12,j,k)−fn(i−12,j,k)]∂f∂y|y=iΔy≈1Δy[fn(i,j+12,k)−fn(i,j−12,k)]∂f∂z|z=iΔz≈1Δz[fn(i,j,k+12)−fn(i−12,j,k−12)]∂f∂t|t=nΔt≈1Δt[fn+12(i,j,k)−fn−12(i,j,k)]. | (4) |
In the two-dimensions case, the facet is located on the plane
| R=|∬z=z0[˜E∗iטHr+˜ErטH∗i]⋅ˆzdxdy∬z=z0[˜E∗iטHi+˜EiטH∗i]⋅ˆzdxdy|, | (5) |
here
An ECL consists of a grating fiber and an LD, and the optical film was produced on the LD’s facet. The physical model of the LD in an ECL is shown in Fig. 1 (a) (color online), and the facet of the LD is shown by the red circle. It can be seen that the facet has a complicated structure (different colors represent different layers), which presents a significant computational resource-intensive issue for FDTD. Therefore, we used a simplified facet model, which highlighted the majority of reflectivity-influencing elements and decreased the need for calculation. This model consists of a low refractive index cladding layer that surrounded a high refractive index core layer as shown in Fig. 1 (b) (color online).
Among the two layers, the core layer represents the active region and the waveguide, which is the area that emits the laser and imposes a substantial impact on reflectivity. Considering single-mode conditions, the total thickness Hcore and width of the core layer
| Parameter | Typical value and range |
| Core layer thickness (Hcore) | 0.5 μm/0.05−1 μm |
| Core layer width (Lcore) | 1 μm/0.2−2 μm |
| Core layer refractive index (ncore) | 3.4902−3.6 |
| Cladding refractive index (nclad) | 3.4902 |
| Refractive index difference ($\Delta n$) | 3% |
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In the experiment, the ECL was made up of a grating fiber and an edge-emitting LD. The LD was created by using a standard procedure and epitaxially grown on a GaAs substrate. The natural cleavage facet of the LD was formed when it was separated into a bar in the air. Then, plasma cleaning and passivation were used to remove the oxides and contaminants from the facet before coating.
The film materials include silicon oxide and niobium oxide, both of which have superior optical qualities and reliability. At 980 nm, their respective refractive indices are 1.45 and 2.20. The LD bars and the GaAs accompanying wafer were concurrently coated with optical films using magnetron sputtering, which was assisted by an Ar ion beam. The film thickness was tracked and controlled in real-time by the crystal control system with an inaccuracy of less than 1 nm. The coated bars were then broken down into LD chips. Six chips were covered with AR film, while another six chips were coated with HR film. To test the optimal design performance, the numbers of chips coated with PWM-designed film were the same for easier comparison.
Despite a variety of direct measurement methods, they are limited by the tiny size and complex structure of the facet[22]. Therefore, the output power of the front and rear facets were measured and compared to estimate the HR film’s reflectivity. Because AR film’s reflectivity is close to 0, it is challenging to measure it using a similar method so the LD's front and rear facets were coated with AR film, which converted the laser into superradiation luminescence. Then, the spectrum was measured to estimate the AR film reflectivity by ripple index.
The size of the facet is small, usually in the scale of μs, and the facet structure is intricate. Therefore, determining whether the optical film designed by PWM can be used with the LD is our first issue. First, we investigated the impact of size using FDTD. The reflectivity at 980 nm for various diameters (Hcore and Lcore) for both AR film and HR film is shown in Fig. 2 (color online). Particularly, for the tiny size, whose reflectivity greatly deviates from the designed value, the reflectivity is not perfect enough. It shows that reflectivity and size have a strong relationship and that different sizes require different film designs.
By analyzing the reflection of AR films with a size that is similar to the ECL used in the experiment, we were able to assess the effect of the film layers and refractive index distribution. The reflection curves of single-layer and double-layer AR films are depicted and contrasted in Fig. 3 (a) and (b) (color online), respectively. For single-layer AR film, the minimum reflectivity is only 0.1%, which is much higher than the designed value, and the curves deviate slightly toward the short wave. This deviation is more prominent in the double-layer AR film, which drifts over 60 nm from its designed value. Additionally, the double-layer AR film's reflectivity is influenced by the refractive index distribution, and it is evident that the linear and parabolic reflection curves do not coincide. All these issues collectively highlight the significant discrepancies between simulation results and designed values. Consequently, the AR film designed by PWM cannot be applied to ECL.
The HR film on LD was examined. Fig. 4 (color online) displays the HR film reflectivity of several HL pairs. It is clearly seen that there is a substantial variation in different refractivity types, and the designed values are higher, regardless of the number of pairs and types of refractive index. The variation also spreads as the number of pairs grows. The source of the variance is explained by the illustration. It can be seen that the reflectivity is 2%−5% lower than the designed value at 980 nm, and other wavelengths see a progressive expansion of this variation, which is inadequate for LDs. According to the simulation, the HR film's reflectivity is less than the design value. It is impractical to blindly raise HL pairs because the variance of reflectivity rises logarithmically. The design of HR film needs to be optimized to increase reflectivity.
Symmetric Optical Cavities (SOC) constitute the foundation of the analysis above while ASOCs are also frequently employed in ECLs. Therefore, the reflectivity of optical film on an SOC and ASOC is compared. Fig. 5 depicts the reflection curves of AR film and HR film, respectively. The thickness ratios of the three typical ASOCs are 40∶60, 25∶75, and 10∶90. For AR film, the lowest reflectivity is only 0.11%, which is 80% higher than its designed value, and the reflectivity is more incorrect when Lcore is small, which is unacceptable for an ECL. Additionally, the reflectivity of AR film on different ASOC types is comparable, but not on HR film. HR films have a significant and even 3% reflectivity variance between distinct ASOCs, and the 10∶90 type has the lowest reflectivity. Similar to AR film, HR film’s reflection on ASOC is worse than the designed value, and optimization of the optical film’s design in the ECL of ASOC is necessary.
The above research demonstrates that the optical film of LD in ECL cannot be designed by PWM. To improve the film design, we employed a model that is compatible with the ECL used in the experiment. We chose film thickness as the scanning parameter since it is easier to manipulate when coating. Fig. 6 (a) and 6(b) (color online) are the sweeps of AR film and HR film, respectively. Nb2O5 and SiO2 arethe first and second layers of the AR film, which is opposite to the structure of the HR film. The equivalent L1 and L2 are in the range of 0.125−0.175 and 0.15−0.225 for areas with reflectivity less than 0.1%. It should be noted that the film thickness is defined here by normalized optical thickness, and the typical film thickness in PWM design is 0.25. In Fig. 6 (b), the thickness range of HR film with high reflectivity can also be determined by using the same method. It is evident that for both AR film and HR film, the thicknesses corresponding to the ideal reflectivity deviate from the PWM designed value, which verifies the previous conclusion.
By scanning the film’s thickness, we were able to determine the range of film thicknesses appropriate for the LD, which served as guide for the following optimization. Then, as illustrated in Fig. 7 (color online), the particle swarm method was applied to further optimize the design. The reflectivities before and after optimization are shown by the black and red lines, respectively. For AR film, the issue of reflection curve deviations toward the short wave is resolved, and the reflectivity decreases to 0.01% at 980 nm. For HR film, the reflectivity is above 95% at a variety of wavelength ranges, more than 6% higher than that before optimization. The reflectivity of the optimization design is significantly better than those of the PWM designs, making it more suitable for ECL.
In this section, the optimized design was experimentally validated and applied to the facet coating of the ECL. Firstly, we tested the film on the accompanying GaAs wafer using the film thickness and reflectivity measuring instrument (Filmetrics F20-EXR). This film is identical to that on the ECL, as shown in Fig. 8 (color online). According to the test results, the reflectivity of the optimized HR and AR films is 0.04% and 97.22% at 980 nm, respectively. It also has a satisfactory reflectivity near 980 nm. This indicates that the coating process has the expected effect and the optical film has perfect reflectivity. However, in reality, the accompanying film does not adequately depict the reflection properties because of variations in the size and structure of the ECL, so further testing is required.
The optical properties and reliability of optical films are greatly impacted by the defects, which directly cause light absorption, loss, and potentially catastrophic optical damage. LD is then destroyed. The film was examined using the optical microscope and Scanning Electron Microscope (SEM), as seen in Fig. 9 (color online). The surface of the optimum film is smooth, and there are no noticeable pits or bumps. It is possible to assume that the coating process is adequate and the optical film is of good quality, meeting the required standards.
It is challenging to precisely measure the film's reflectivity due to its minuscule size and intricate structure. We employed an indirect measurement method which was split into two components. For HR film measurement, the front facet of the LD was uncoated and the rear facet was coated with HR film. According to the known reflectivity of the uncoated front facet, the reflectivity of HR film was calculated by comparing the output powers of the front facet and the rear facet, as illustrated in Fig. 10(a) (color online). The power radio is essentially the inverse of the transmittance of the front and rear facets. All the ratios of the 12 chips are shown in Fig. 10(b) (color online). The average ratio is nearly 7% higher on average compared to LD without optimization. Considering the loss and absorption, the reflectivity of the optimized HR film exceeds 96%, which is consistent with the simulation results. And that the increased LD power further supports this conclusion.
For AR film with a small reflectivity, the above measurement method is no longer applicable due to the fatal effect of facet loss and absorption. Therefore, we used another indirect measurement method that involves coating AR films on both the front and rear facets and measuring the superradiation spectrum. The relative intensity of the film's reflectivity can then be qualitatively examined by computing the ripple index, which is directly connected to the reflectivity. Fig. 11 (a) (color online) displays the superradiation spectrum. After optimization, the ripple number and strength are suppressed, which results in a decrease in the ripple index, and indicates that the AR film's reflectivity decreases. The ripple index of various chips was then counted, as seen in Fig. 11 (b) (color online). The average ripple intensity is nearly a 30% reduction from the 0.1 dB recorded before optimization. Therefore, the reflectivity of optimized AR film also decreased. In fact, the reflectivity of the optimized film is lower when taking into account the film's absorption and other losses. As a result, the optimized AR film has likewise attained a reasonable reflectivity, supporting the assertion that the optimized design is more suited for an ECL.
The above results verified the optimized design of AR and HR film, and the reflection characteristics significantly improved after optimization. The optimized films were applied to the ECL, and the ECL's pigtail output power and spectrum were measured, as shown in Fig. 12 (color online). In the Power-Current-Voltage (PIV) curves, there is no kink in the power curve within 0−800 mA, and the power exceeds 650 mW after package. ECL maintains high output power after optimization. The tests above demonstrated the preferable output characteristics of ECLs coated with optimized optical film.
To supply ECLs with suitable optical films, FDTD was used to accurately analyze and optimize films. The influence of dimensions and structure including core-layer size, refractive index distribution, and asymmetric structure, which are significant to practical devices, were taken into consideration. Simulation results show that PWM designs are unsuitable for LD because they suffer from problems that include reflection curve shifts, poor reflectivity, and narrow bandwidth. Mainly, the reflectivity differs significantly from the designed value. By scanning the film thickness, the corresponding thickness range of low reflectivity was determined, and the particle swarm algorithm was used to optimize the film within this range. The reflectivity of AR film is reduced by the optimized design to 0.01 %, whereas the reflectivity of HR film is over 95% after optimization.
The optical film was made by magnetron sputtering, and the film's morphology satisfied the criteria. Numerous measurements on the reflectivity of the optimized films were conducted. The reflectivity of AR film and HR film on the GaAs accompanying wafer is 0.04% and 97.22% respectively. According to the indirect measurement of the optical film on the LD’s facet, the reflectivity of the optimized AR film has been reduced by 30%, while the reflectivity of the optimized HR film increased to over 96%. These measurements confirmed the effectiveness of the optimized design. The optimized films were then used with the ECL and demonstrated excellent performance with a power of greater than 650 mW. In this study, we have designed and fabricated the optical film for an ECL with good optical properties, and obtained an ECL with excellent performance.
| [1] |
CUI Q, LEI Y X, CHEN Y Y, et al. Advances in wide-tuning and narrow-linewidth external-cavity diode lasers[J]. Science China Information Sciences, 2022, 65(8): 181401. doi: 10.1007/s11432-021-3454-7
|
| [2] |
SWINT R. Scattering loss at waveguide facets and implications for laser efficiency[C]. 2018 IEEE International Semiconductor Laser Conference (ISLC), IEEE, 2018: 1-2.
|
| [3] |
ZHANG S Y, FENG S W, ZHANG Y M, et al. Monitoring of early catastrophic optical damage in laser diodes based on facet reflectivity measurement[J]. Applied Physics Letters, 2017, 110(22): 223503. doi: 10.1063/1.4984598
|
| [4] |
MROZIEWICZ B. External cavity wavelength tunable semiconductor lasers-a review[J]. Opto-Electronics Review, 2008, 16(4): 347-366.
|
| [5] |
PIEGARI A, FLORY F. Optical Thin Films and Coatings: From Materials to Applications[M]. 2nd ed. Sawston, Cambridge: Woodhead Publishing, 2018: 26-52.
|
| [6] |
MOAYEDFAR M, ASSADI M K. Various types of anti-reflective coatings (ARCS) based on the layer composition and surface topography: a review[J]. Reviews on Advanced Materials Science, 2018, 53(2): 187-205. doi: 10.1515/rams-2018-0013
|
| [7] |
YUAN H, SUN CH ZH, XU J M, et al. Design and fabrication of multilayer antireflection coating for optoelectronic devices by plasma enhanced chemical vapor deposition[J]. Acta Physica Sinica, 2010, 59(10): 7239-7244. (in Chinese) doi: 10.7498/aps.59.7239
|
| [8] |
GHADIMI-MAHANI A, FARSAD E, GOODARZI A, et al. Improvement and characterization of high-reflective and anti-reflective nanostructured mirrors by ion beam assisted deposition for 944 nm high power diode laser[J]. Optics Communications, 2015, 355: 94-102. doi: 10.1016/j.optcom.2015.06.021
|
| [9] |
IKEGAMI T. Reflectivity of mode at facet and oscillation mode in double-heterostructure injection lasers[J]. IEEE Journal of Quantum Electronics, 1972, 8(6): 470-476. doi: 10.1109/JQE.1972.1077091
|
| [10] |
SHIBAYAMA J, MURAKI M, YAMAUCHI J, et al. Efficient implicit FDTD algorithm based on locally one-dimensional scheme[J]. Electronics Letters, 2005, 41(19): 1046-1047. doi: 10.1049/el:20052381
|
| [11] |
NGUYEN T G, MITCHELL A. Analysis of optical waveguides with multilayer dielectric coatings using plane wave expansion[J]. Journal of Lightwave Technology, 2006, 24(1): 635-642. doi: 10.1109/JLT.2005.860158
|
| [12] |
REED M, BENSON T M, KENDALL P C, et al. Antireflection-coated angled facet design[J]. IEE Proceedings - Optoelectronics, 1996, 143(4): 214-220. doi: 10.1049/ip-opt:19960597
|
| [13] |
TORABI A, SHISHEGAR A A, FARAJI-DANA R. Analysis of modal reflectivity of optical waveguide end-facets by the characteristic Green’s function technique[J]. Journal of Lightwave Technology, 2014, 32(6): 1168-1176. doi: 10.1109/JLT.2013.2297891
|
| [14] |
LABUKHIN D, LI X. Three-dimensional finite-difference time-domain simulation of facet reflection through parallel computing[J]. Journal of Computational Electronics, 2005, 4(1-2): 15-19. doi: 10.1007/s10825-005-7099-4
|
| [15] |
TANG L, TSUI K H, LEUNG S F, et al. Large-scale, adhesive-free and omnidirectional 3D nanocone anti-reflection films for high performance photovoltaics[J]. Journal of Semiconductors, 2019, 40(4): 042601. doi: 10.1088/1674-4926/40/4/042601
|
| [16] |
GUO X, LIU Q L, TIAN H J, et al. Optimization of broadband omnidirectional antireflection coatings for solar cells[J]. Journal of Semiconductors, 2019, 40(3): 032702. doi: 10.1088/1674-4926/40/3/032702
|
| [17] |
JIANG A Q, OSAMU Y, CHEN L Y. Multilayer optical thin film design with deep Q learning[J]. Scientific Reports, 2020, 10(1): 12780. doi: 10.1038/s41598-020-69754-w
|
| [18] |
TRAN V T, VAN MAI H, NGUYEN H M, et al. Machine-learning reinforcement for optimizing multilayered thin films: applications in designing broadband antireflection coatings[J]. Applied Optics, 2022, 61(12): 3328-3336. doi: 10.1364/AO.450946
|
| [19] |
YANG L M, PAN C Y, LU F P, et al. Anti-reflection sub-wavelength structures design for InGaN-based solar cells performed by the finite-difference-time-domain (FDTD) simulation method[J]. Optics &Laser Technology, 2015, 67: 72-77.
|
| [20] |
SARKAR D. FDTD Analysis of Guided Electromagnetic Wave Interaction with Time-Modulated Dielectric Medium[M]. Singapore: Springer, 2022.
|
| [21] |
JIANG H L, WU L T, ZHANG X G, et al. Computationally efficient CN-PML for EM simulations[J]. IEEE Transactions on Microwave Theory and Techniques, 2019, 67(12): 4646-4655. doi: 10.1109/TMTT.2019.2946160
|
| [22] |
PRUSZYŃSKA-KARBOWNIK E, MROZIEWICZ B. Measurements and analysis of antireflection coatings reflectivity related to external cavity lasers[J]. Optics Communications, 2011, 284(1): 373-375. doi: 10.1016/j.optcom.2010.08.062
|
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Figures(12) / Tables(1)
YOU Dao-ming, TAN Man-qing, GUO Wen-tao, CAO Ying-chun, WANG Zi-jie, YANG Qiu-rui, WAN Li-li, WANG Xin, LIU Heng. Design and fabrication of an optical film for fiber bragg grating external cavity diode lasers[J]. Chinese Optics, 2023, 16(2): 447-457. doi: 10.37188/CO.EN.2022-0010
| Parameter | Typical value and range |
| Core layer thickness (Hcore) | 0.5 μm/0.05−1 μm |
| Core layer width (Lcore) | 1 μm/0.2−2 μm |
| Core layer refractive index (ncore) | 3.4902−3.6 |
| Cladding refractive index (nclad) | 3.4902 |
| Refractive index difference ($\Delta n$) | 3% |
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