SiC-Based Materials and Devices Enabling Electrification and Mobility at Scale May 29, 2020 Exhibit 99.1

II-VI Incorporated Q3 FY2020 Overview 18 Countries 69 Locations 22,000+ Employees $388M Cash and Equivalents $627M Revenue $120M YTD Cash Flow from Operations Revenue by End Markets 5% Semi. Cap. Equip. 2% Life Science 6% Consumer Electronics 1% Other Communications Industrial 7% Military Revenue by Regions Japan Other North America Europe China “TWO SIX” Refers to groups II and VI of the Periodic Table of Elements Core Competency: ENGINEERED MATERIALS

Core Strategy Diversified per Platform Capital Intensive Markets A Leader in engineered materials and optoelectronic devices Differentiated lasers, optics, and integrated circuits Enabling the convergence of communications, computing, and sensing Infrastructure Core Competency Innovation Strategy Engineered Materials Differentiation Valued By Customers Performance Process Intensive Products

Aerospace & Defense RF and Power Electronics Optical Communications 3D Sensing & LiDAR $7.5B CY25 Market For 3D sensing in consumer electronics & LiDAR in automotive For terrestrial, undersea, wireless optical infrastructure and datacenters 14% CY20-25 CAGR $6.2B For electric vehicles, smart power grids and 4G/5G RF antennas 24% For F35, contested space, directed energy and hypersonics $22B 24% GaAs | InP | LCoS GaAs | InP GaAs | Sapphire Source: Ovum, LightCounting, Cignal AI, Internal Estimates $2.6B 15% SiC | GaN/SiC | Diamond Addressing Multiple Strong and Growing Markets Source: Morgan Stanley, Forbes, Yole, IDC Source: Yole, Strategy Analytics, LightCounting (includes devices) Source: Internal estimates Updated on 4/9/2020

Easton, PA, USA SiC Substrates (RF and Power) Crystal growth Ongoing Expansion > 250K sq.ft. space Strategic Compound Semiconductor Platforms: SiC and GaN II-VI will be a key enabler of SiC and GaN compound semiconductor technology nodes Leading technology, vertical integration, scalable 150mm platform, supply chain security 5G wireless, green energy, EV/HEV Pine Brook, NJ, USA SiC Substrates (RF and Power) R&D Crystal growth Slicing Champaign, IL, USA GaN and SiC EpiWafers GaN/SiC RF SiC/SiC Power Ongoing Expansion Starkville, MS, USA Back End SiC Wafer Processing Polish Clean Characterize Ship RF & Power Market Warren, NJ, USA RF GaN/SiC Devices GaN/SiC RF HEMT’s

II-VI SiC Diameter Expansion Timeline Advantages of Large Diameter Substrates Large diameter substrate fabrication cost (per unit area) is reduced significantly Large diameter wafer availability has helped move SiC-based devices from niche to mainstream Existing 200 mm silicon wafer fab lines can be used for SiC devices manufacturing 2’’ Wafer Manufacturing 3’’ Wafer Manufacturing 100 mm Wafer Demonstrated High Quality Wafer Manufacturing 150 mm Wafer Demonstrated Manufacturing 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 World First 200 mm Wafer Demonstrated 4H n-Type 6H SI Major Capacity Expansion

SiC Manufacturing Capacity Expansion Relative Quantity of Substrates Doubled Capacity Every 18-24 Months Actual Projected Calendar Year 5-10x Capacity Increase Over the Next 5 Years

Remote Radio Head Beam-forming Antenna 5G WIRELESS 4G WIRELESS Bi-Directional Converter/ Inverter/ Electric Motor DC-DC Converter Electric Charger / HV Battery Enabling Electrification & Mobility EV/HEV GREEN ENERGY Solar & Wind Energy Smart Grid Power Switching Ramping silicon carbide substrate capacity 5-10x over the next 5 years 100, 150 mm diameter conductive substrates 2015: World’s first 200 mm conductive substrates For SiC MOSFETs power devices About 10% more driving distance on the same charge POWER ELECTRONICS FOR ELECTRIC VEHICLES 100, 150 mm diameter semi-insulating substrates 2019: Word’s first 200 mm semi-insulating substrates For SiC-based GaN HEMT devices GaN/SiC enables high-bandwidth 5G bands RF ELECTRONICS FOR WIRELESS BASE STATIONS