1. “Homodyne Spectroscopy with Broadband Terahertz Power Detector Based on 90-nm Silicon CMOS Transistor”
by Ikamas, K.; But, D.; Lisauskas, A.
Appl. Sci. 2021, 11(1), 412; https://doi.org/10.3390/app11010412
Available online: https://www.mdpi.com/2076-3417/11/1/412

2. “Beam Profile Characterisation of an Optoelectronic Silicon Lens-Integrated PIN-PD Emitter between 100 GHz and 1 THz”
by Smith, J.; Naftaly, M.; Nellen, S.; Globisch, B.
Appl. Sci. 2021, 11(2), 465; https://doi.org/10.3390/app11020465
Available online: https://www.mdpi.com/2076-3417/11/2/465

3. “Trends in Performance Limits of the HOT Infrared Photodetectors”
by Rogalski, A.; Martyniuk, P.; Kopytko, M.; Hu, W.
Appl. Sci. 2021, 11(2), 501; https://doi.org/10.3390/app11020501
Available online: https://www.mdpi.com/2076-3417/11/2/501

4. “Performance Evaluation of a THz Pulsed Imaging System: Point Spread Function, Broadband THz Beam Visualization and Image Reconstruction”
by Di Fabrizio, M.; D’Arco, A.; Mou, S.; Palumbo, L.; Petrarca, M.; Lupi, S.
Appl. Sci. 2021, 11(2), 562; https://doi.org/10.3390/app11020562
Available online: https://www.mdpi.com/2076-3417/11/2/562

5. “Inductive Thermography as Non-Destructive Testing for Railway Rails”
by Tuschl, C.; Oswald-Tranta, B.; Eck, S.
Appl. Sci. 2021, 11(3), 1003; https://doi.org/10.3390/app11031003
Available online: https://www.mdpi.com/2076-3417/11/3/1003

6. “Review on Complete Mueller Matrix Optical Scanning Microscopy Imaging”
by Le Gratiet, A.; Mohebi, A.; Callegari, F.; Bianchini, P.; Diaspro, A.
Appl. Sci. 2021, 11(4), 1632; https://doi.org/10.3390/app11041632
Available online: https://www.mdpi.com/2076-3417/11/4/1632

7. “Cladding-Pumped Erbium/Ytterbium Co-Doped Fiber Amplifier for C-Band Operation in Optical Networks”
by Supe, A.; Olonkins, S.; Udalcovs, A.; Senkans, U.; Mūrnieks, R.; Gegere, L.; Prigunovs, D.; Grube, J.; Elsts, E.; Spolitis, S.; Ozolins, O.; Bobrovs, V.
Appl. Sci. 2021, 11(4), 1702; https://doi.org/10.3390/app11041702
Available online: https://www.mdpi.com/2076-3417/11/4/1702

8. “Dual-Slope Diffuse Reflectance Instrument for Calibration-Free Broadband Spectroscopy”
by Blaney, G.; Donaldson, R.; Mushtak, S.; Nguyen, H.; Vignale, L.; Fernandez, C.; Pham, T.; Sassaroli, A.; Fantini, S.
Appl. Sci. 2021, 11(4), 1757; https://doi.org/10.3390/app11041757
Available online: https://www.mdpi.com/2076-3417/11/4/1757

9. “Storm-Time Features of the Ionospheric ELF/VLF Waves and Energetic Electron Fluxes Revealed by the China Seismo-Electromagnetic Satellite”
by Zhima, Z.; Hu, Y.; Shen, X.; Chu, W.; Piersanti, M.; Parmentier, A.; Zhang, Z.; Wang, Q.; Huang, J.; Zhao, S.; Yang, Y.; Yang, D.; Sun, X.; Tan, Q.; Zhou, N.; Guo, F.
Appl. Sci. 2021, 11(6), 2617; https://doi.org/10.3390/app11062617
Available online: https://www.mdpi.com/2076-3417/11/6/2617

10. “Inverse Design for Silicon Photonics: From Iterative Optimization Algorithms to Deep Neural Networks”
by Mao, S.; Cheng, L.; Zhao, C.; Khan, F.; Li, Q.; Fu, H.
Appl. Sci. 2021, 11(9), 3822; https://doi.org/10.3390/app11093822
Available online: https://www.mdpi.com/2076-3417/11/9/3822

11. “A Survey of Low-Cost 3D Laser Scanning Technology”
by Bi, S.; Yuan, C.; Liu, C.; Cheng, J.; Wang, W.; Cai, Y.
Appl. Sci. 2021, 11(9), 3938; https://doi.org/10.3390/app11093938
Available online: https://www.mdpi.com/2076-3417/11/9/3938

12. “Towards a Glass New World: The Role of Ion-Exchange in Modern Technology”
by Berneschi, S.; Righini, G.; Pelli, S.
Appl. Sci. 2021, 11(10), 4610; https://doi.org/10.3390/app11104610
Available online: https://www.mdpi.com/2076-3417/11/10/4610

13. “Trace CH4 Gas Detection Based on an Integrated Spherical Photoacoustic Cell”
by Jiao, Y.; Fan, H.; Gong, Z.; Yang, K.; Shen, F.; Chen, K.; Mei, L.; Peng, W.; Yu, Q.
Appl. Sci. 2021, 11(11), 4997; https://doi.org/10.3390/app11114997
Available online: https://www.mdpi.com/2076-3417/11/11/4997

14. “Gas Sensors Based on Localized Surface Plasmon Resonances: Synthesis of Oxide Films with Embedded Metal Nanoparticles, Theory and Simulation, and Sensitivity Enhancement Strategies”
by Rodrigues, M.; Borges, J.; Lopes, C.; Pereira, R.; Vasilevskiy, M.; Vaz, F.
Appl. Sci. 2021, 11(12), 5388; https://doi.org/10.3390/app11125388
Available online: https://www.mdpi.com/2076-3417/11/12/5388

15. “From Femtoseconds to Hours—Measuring Dynamics over 18 Orders of Magnitude with Coherent X-rays”
by Lehmkühler, F.; Roseker, W.; Grübel, G.
Appl. Sci. 2021, 11(13), 6179; https://doi.org/10.3390/app11136179
Available online: https://www.mdpi.com/2076-3417/11/13/6179

16. “Terahertz and Microwave Optical Properties of Single-Crystal Quartz and Vitreous Silica and the Behavior of the Boson Peak”
by Naftaly, M.; Gregory, A.
Appl. Sci. 2021, 11(15), 6733; https://doi.org/10.3390/app11156733
Available online: https://www.mdpi.com/2076-3417/11/15/6733

17. “Exact Scan Patterns of Rotational Risley Prisms Obtained with a Graphical Method: Multi-Parameter Analysis and Design”
by Duma, V.; Dimb, A.
Appl. Sci. 2021, 11(18), 8451; https://doi.org/10.3390/app11188451
Available online: https://www.mdpi.com/2076-3417/11/18/8451

18. “Review of Element Analysis of Industrial Materials by In-Line Laser—Induced Breakdown Spectroscopy (LIBS)”
by Pedarnig, J.; Trautner, S.; Grünberger, S.; Giannakaris, N.; Eschlböck-Fuchs, S.; Hofstadler, J.
Appl. Sci. 2021, 11(19), 9274; https://doi.org/10.3390/app11199274
Available online: https://www.mdpi.com/2076-3417/11/19/9274

19. “Fast Image Reconstruction Technique for Parallel Phase-Shifting Digital Holography”
by Tsuruta, M.; Fukuyama, T.; Tahara, T.; Takaki, Y.
Appl. Sci. 2021, 11(23), 11343; https://doi.org/10.3390/app112311343
Available online: https://www.mdpi.com/2076-3417/11/23/11343

20. “Experimental Demonstration and Performance Enhancement of 5G NR Multiband Radio over Fiber System Using Optimized Digital Predistortion”
by Hadi, M.; Awais, M.; Raza, M.; Ashraf, M.; Song, J.
Appl. Sci. 2021, 11(24), 11624; https://doi.org/10.3390/app112411624
Available online: https://www.mdpi.com/2076-3417/11/24/11624