Filed by Finisar Corporation

Pursuant to Rule 425 Under the Securities Act of 1933

And deemed filed pursuant to Rule 14a-12

Under the Securities Exchange Act of 1934

Subject Company: Finisar Corporation

Commission File No. 000-27999

II-VI to Acquire Finisar Creates a Global Leader in Photonics and Compound Semiconductors November 9, 2018

Safe Harbor Statement Page 2 This communication contains “forward-looking statements” within the meaning of the federal securities laws, including Section 27A of the Securities Act of 1933 and Section 21E of the Securities Exchange Act of 1934. Forward-looking statements often address expected future business and financial performance and financial condition, and often contain words such as “expect,” “anticipate,” “intend,” “plan,” “believe,” “seek,” “see,” “will,” “would,” “target,” similar expressions, and variations or negatives of these words. Forward-looking statements are not guarantees of future results and are subject to risks, uncertainties and assumptions that could cause actual results to differ materially from those expressed in any forward-looking statements. Important factors that may cause such a difference include: (i) the ability of II-VI Incorporated (“II-VI”) and Finisar Corporation (“Finisar”) to complete the proposed transaction on the anticipated terms and timing or at all, (ii) potential litigation relating to the proposed transaction, (iii) inherent risks and costs associated with the integration of the businesses and achievement of the anticipated synergies, (iv) potential disruptions from the proposed transaction that may harm the parties’ respective businesses, (v) the ability of the parties to retain and hire key personnel, (vi) adverse legal and regulatory developments or determinations that could delay or prevent completion of the proposed transaction, and (vii) the ability of II-VI to consummate financing related to the transaction. Additional risks are described under the heading “Risk Factors” in II-VI’s Annual Report on Form 10-K for the year ended June 30, 2018, filed with the U.S. Securities and Exchange Commission (the “SEC”) on August 28, 2018, and in Finisar’s Annual Report on Form 10-K for the year ended April 29, 2018, filed with the SEC on June 15, 2018. These risks, as well as other risks associated with the proposed transaction, will be more fully discussed in a joint proxy statement/prospectus that will be included in a registration statement on Form S-4 to be filed by II-VI with the SEC in connection with the proposed transaction. Neither II-VI nor Finisar assumes any obligation to publicly provide revisions or updates to any forward looking statements, whether as a result of new information, future developments or otherwise, should circumstances change, except as otherwise required by securities and other applicable laws.

A Transformative Combination Communications, Automotive, Consumer Electronics, Materials Processing, Semiconductor Equipment, Military, Life Sciences End Markets $2.5B Pro Forma Revenue1 $570M Pro Forma EBITDA1 $22B Addressable Market2 70 Locations Worldwide Diversified Global Footprint 24K+ Employees Worldwide Note: Pro forma Revenue and EBITDA represents LTM 09/30/2018 for II-VI and LTM 07/29/2018 for Finisar. 1. Represents LTM 09/30/2018 for II-VI plus LTM 07/29/2018 for Finisar and includes $150mm run-rate synergies for EBITDA. EBITDA excludes amortization of intangibles, the impact of SFAS 123(R) stock-based compensation expense and one-time charges. 2022 estimated market size. Includes 3D Sensing, Power Devices for Automotive and Wireless RF size from Yole, Optical Communications from Lightcounting and Ovum, Industrial Processing, Military, Life Sciences from Strategies Unlimited. 2. Page 3

Finisar at a Glance #1 Optical Components Market Leader Leading GaAs Platform for 3D Sensing and LiDAR Broadest portfolio of optical modules Differentiation via Vertical Integration Engineering Innovation with ~2,000 Patents Page 4  Enables 3D Sensing for consumer and automotive applications  Key product: VCSEL arrays  Enables optimal transmission in access, metro and long-haul  Key products include WSS, OCMs, and tunable/coherent modules  Enables data center and enterprise network connectivity  Key products include transceivers for 25G, 100G and 400G 3D SENSING TELECOM DATACOM

Strategic Window of Opportunity Now Combined broad base of talent, technology and manufacturing enhances our ability to hit market windows today Right Technology + Right Team + Right Time TAM ($B) $20 Disruptive Megatrends Inflection Point CAGR 20% $15 Proliferation of Cloud Services Electric & Autonomous Vehicles $10 3D Sensing Window of Opportuni $5 $-Growth in Mobile & 5G Communications Increased Data and Video Consumption 2018 2019 2020 2021 RF Electronics 2022 Power Electronics Datacom TRxTelecom TRxROADM3DS & LiDAR Note: Market size forecast from Lightcounting, Ovum and Yole. Page 5 CAGR 16% ty1

II-VI and Finisar: History of Shared Culture and Values Quality Culture is Foundational Shared Value and Vision  30+ Years of Innovation with over 2,700 patents  Commitment to Address Customer Needs from a Broad Product Portfolio  Leaders in Engineered Materials & Optoelectronic Devices Shared Model  Selective & Strategic Acquisitions  Successful Differentiation via Vertical Integration  Sustained Market Leadership The Perfect Match: History, Culture, Technology and Assets Page 6

Transaction Strategic Rationale Creates One of the Largest Photonics and Compound Semiconductor Companies with $2.5B of Revenue1 Combination Addresses Multiple Strong and Growing Markets Complementary Expertise in Datacom & Telecom Strengthens Position in Optical Communications Creates the Most Compelling 3D-Sensing and LiDAR platform with Faster Time to Market A Leader in Engineered Materials and Compound Semiconductors Expected to Achieve $150mm Run-Rate Cost Synergies within 36 months 1. Represents LTM 9/30/2018 for II-VI plus LTM 07/29/2018 for Finisar. Page 7

One of the Largest Photonics & Compound Semiconductor Companies1 $2,547 $2,504 $1,212 $183 + Note: Dollars in millions. Lumentum pro forma for Oclaro. MKS pro forma for ESIO. 1. Represents LTM Revenue. Page 8 $1,931 $1,902 $1,542 $1,491 $1,292 $319 $308 $294

Irreversible Megatrends I Addressing Multiple Strong and Growing Markets 3D Sensing & LiDAR Optical Communications RF Electronics in Wireless & Military Power Electronics For Green Energy For electric vehicles (EV/HEV), smart grid power switching, solar and wind energy For 3D sensing in consumer electronics & LiDAR in automotive For terrestrial, submarine & wireless optical infrastructure and datacenters For 4G remote radio heads, 5G beam forming antennas & RF military electronics $1.1B 2022 Market 2018-22 CAGR $2.9B $12.1B $1.2B 60% 13% 26% 27% Source: 3D Sensing & LiDAR, Wireless RF and Power Electronics for Green Energy from Yole, Optical Communications from Lightcounting and Ovum. Page 9 GaAs | GaN/SiC | Diamond SiC GaAs | InP GaAs | InP | Si Photonics

Complementary Expertise in Telecom and Datacom      Industry leader in Datacom transceivers for Hyperscale datacenters Fixed & tunable transceivers for access & wireless optical infrastructure Next-generation coherent transmission & submarine amplification ROADM for optical transport: WSS, optical amplifiers, optical monitoring Highly vertically integrated from engineered materials to subsystems Pump Laser Transceiver Amplifier Wavelength Selective Switch Product Portfolio Across Market Segments Page 10

Most Compelling Platform for 3D Sensing & LiDAR II-VI’s and Finisar's GaAs and InP Platforms = Enhanced competency in 3D Sensing and LiDAR  Optimization of R&D, Capital and Asset Utilization = Faster Time to Market  Vertically integrated 6 inch GaAs compound semiconductor platform, one of the largest in the world = RF Devices and advanced optoelectronic integration VCSEL Arrays 940nm DFB Lasers3D Sensing Filters Wide Angle Mirror VCSEL Arrays For 3D Sensing & LiDAR CAGR (’18-22): +60% Source: Yole Page 11

RF Electronics for Wireless Infrastructure & Military  II-VI’s GaAs & SiC on 6” platform + Finisar’s microelectronics design expertise = Access to larger & growing markets  Collaboration with SEDI for GaN/SiC RF electronics  For wireless & military: efficient, high power RF amplification with GaN/SiC HEMT  Thin-film diamond on silicon for next generation high speed wireless electronics SiC Substrates GaAs Epiwafers GaAs pHEMT 5G WIRELESS Beam-forming Antenna For 4G & 5G Wireless Antennas For RF Devices in Wireless Handsets For RF Applications in Military & Wireless 4G WIRELESS A world leading supplier of SiC substrates GaN/SiC for RF Electronics Market CAGR (‘18-’22): 26% Source: Yole Remote Radio Head Page 12

Power Electronics for Green Energy  II-VI’s SiC on 6” platform + Finisar’s microelectronics design expertise = Access to larger & growing markets  High efficiency voltage and power conversion = SiC MOSFETs for Green Energy Applications  Electric cars (EV/HEV)  Solar & Wind Energy  Smart Grid Power Switching A world leading supplier of SiC substrates SiC for High Power Electronics Market CAGR (’18-’22): 27% Source: Yole HV Battery Electric Charger Bi-Directional Converter/ Inverter/ Electric Motor DC-DC Converter Page 13

Combined Global Fab Footprint Newton Aycliffe, UK 319,000 sq. ft. Zurich, Switzerland 117,000 sq. ft GaAs - 6 inch Jarfalla, Sweden 26,000 sq. ft InP - 3 inch Champaign, IL, USA 69,000 sq. ft. Epiwafers GaAs, InP, GaN up to 6 inch GaAs - 6 inch Warren, NJ, USA 159,000 sq. ft. GaAs, GaN - 6 inch Allen, TX, USA 160,000 sq. ft. GaAs - 4 Inch Sherman, TX, USA 540,000 sq. ft. GaAs - 6 Inch Fremont, CA, USA 68,000 sq. ft. InP - 3 inch     A broad compound semiconductor technology platform encompassing GaAs, InP, SiC & GaN One of the world’s largest 6-inch vertically integrated epitaxial growth and device fabrication manufacturing platforms A global world-class team of experts and innovators in engineered materials, laser device design & fabrication infrastructure Combined, the companies will offer highly differentiated products & manufacturing scale to serve fast growing markets Page 14

Significant Value Creation Potential from Synergies Annual Estimated Synergies Achieved Within 36 months   Supply chain management - Procurement Infeed - Internal supply of enabling materials and components Cost of Goods Sold   More efficient R&D with scale Complementary engineering and design teams Research & Development   Consolidation of overlapping corporate costs Optimization of operating model General & Administration  Sales & Marketing Savings from scale Total Page 15 ~$150 million ~$65 million ~$85 million

Transaction Overview  Approximately $3.2 billion of total equity value – Finisar shareholders to own approximately 31% of the combined company Transaction Consideration  $26.00 per share – $15.60 in cash and 0.2218 shares of II-VI common stock, valued at $10.40 per share based on the closing price of II-VI’s common stock of $46.88 on November 8, 2018 Per Share Consideration    $2.0 billion of new funded debt in the form of fully committed financing (in addition to unfunded revolver) $1.0 billion of combined balance sheet cash $1.4 billion of equity issued to Finisar shareholders Sources of Financing   Approval by II-VI and Finisar shareholders Regulatory approvals Approval Process  Middle of calendar year 2019, subject to customary closing conditions Expected Timeline   $150mm of expected annual cost synergies realized within 36 months of close Expected to drive accretion in Non-GAAP earnings-per-share for the first full year post close of approximately 10% and more than double that thereafter Financial Highlights Page 16

Transaction Financing  Transaction Financing $2.0 billion new funded debt, fully underwritten by BofA Merrill Lynch – $450 million revolver unfunded at close Pro-forma Capitalization Statistics    Taken together, company has EBITDA generation of $570mm1 Combined company has a strong deleveraging profile Ongoing ability to maximize strategic opportunities Deleveraging and Capital Allocation 1. Represents LTM 09/30/2018 for II-VI and LTM 07/29/2018 for Finisar and includes $150mm run-rate synergies. EBITDA excludes amortization of intangibles, the impact of SFAS 123(R) stock-based compensation expense and one-time charges. Page 17 ($ in billion) x LTM EBITDA (w/ synergies)1 Gross Debt $2.4 4.1x Cash $0.3 0.6x Net Debt $2.0 3.5x

[LOGO]